Fluids Analysis

Interpretation Guide S•O•S

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Optimizing Oil Change Intervals All Caterpillar Diesel Engines except On-Highway Truck Engines

Confidential

This publication is intended for the use of authorized Caterpillar dealers only. Any distribution

of this form to unauthorized personnel must be avoided to maintain Caterpillar leadership in the fluids analysis field.

Contents Notice ………………………………………………………………………………………………..3

Section 1-----Introduction Why Manage Oil Change Intervals?………………………………………………………………4 Taking a Leadership Role………………………………………………………………………….4 What Your Customer Must Do……………………………………………………………………..4 Risk vs. Reward……………………………………………………………………………………..5 Oil Change Interval Optimization Cost Savings Estimation…………………….………………6 Section 2 --- Optimizing Oil Change Intervals ---Diesel Engines Text from Customer Publication PEDP7035……………………………………….…………….9 Section 3 --- Summary of Procedures…………………………………………………………...15 Section 4 --- Factors Affecting Oil Performance and Engine Wear Fixed Factors……………………………………………………………………………………….17 Engine Design……………………………………………………………………………………17 API Ratings and Caterpillar PC Engines………………………………………………………18 API Ratings and Caterpillar DI Engines……………………………………………………….18 Variable Factors……………………………………………………………………………………19

Section 5 --- Variable Factors Defined Managing Oil Change Intervals…………………………………………………………………..21 Maintenance Oil Type…………………………………………………………………………………………...21 Plugged Air Filters……………………………………………………………………………….22

Engine Fuel System Settings…………………………………………………………………..22 Extended Oil Changes………………………………………………………………………….22 Cooling System………………………………………………………………………………….22 Fuel Sulfur………………………………………………………………………………………..22 Application Geographic Location/Client…………………………………………………………………….22 Operating Procedures…………………………………………………………………………..23 Severe/Improper Operation…………………………………………………………………….23 High Operating Temperatures…………………………………………………….……………23 Oil Condition Oxidation………………………………………………………………………………………….23 Soot…………………………………………………………………………………….………….25 Sulfation…………………………………………………………………………………………..26 Nitration……………………………………………………………………………….…………..27 Viscosity…………………………………………………………………………………………..28 External Contamination Milling and Repair Debris……………………………………………………………………….29 Solvents/Sealants/Greases……………………………………………………………………..29 Lacquering………………………………………………………………………………………..30 Agglomerated Soot………………………………………………………………….…………..30 Water and Coolant………………………………………………………………………………30 Glycol……………………………………………………………………………………………...30 Fuel………………………………………………………………………………………………..31 Dirt…………………………………………………………………………………………………31 Oil Transfer……………………………………………………………………………………….32 Internal Contamination Normally Generated Debris…………………………………………………………………….32 Abnormally Generated Debris…………………………………………………….……………32

Engine Fuel System Settings…………………………………………………………………..22 Extended Oil Changes………………………………………………………………………….22 Cooling System………………………………………………………………………………….22 Fuel Sulfur………………………………………………………………………………………..22

Application Geographic Location/Client……………………………………………………………………..22 Operating Procedures…………………………………………………………………………...23 Severe/Improper Operation…………………………………………………………………….23 High Operating Temperatures…………………………………………………….……………23 Oil Condition Oxidation………………………………………………………………………………………….23 Soot…………………………………………………………………………………….………….25 Sulfation…………………………………………………………………………………………..26 Nitration……………………………………………………………………………….…………..27 Viscosity…………………………………………………………………………………………..28 External Contamination Milling and Repair Debris……………………………………………………………………….29 Solvents/Sealants/Greases……………………………………………………………………..29 Lacquering………………………………………………………………………………………..30 Agglomerated Soot………………………………………………………………….…………..30 Water and Coolant………………………………………………………………………………30 Glycol……………………………………………………………………………………………...30 Fuel………………………………………………………………………………………………..31 Dirt…………………………………………………………………………………………………31 Oil Transfer……………………………………………………………………………………….32 Internal Contamination Normally Generated Debris…………………………………………………………………….32 Abnormally Generated Debris…………………………………………………….……………32

Section 6 --- Controlling the Variables A Checklist Engines……………………………………………………………………………….…………..36 Optimally Tuned Engines………………………………………………………….……………36 Oil………………………………………………………………………………………………….36 Oil Filters………………………………………………………………………………………….36 Fuel…………………………………………………………………………………….………….36 Cooling System…………………………………………………………………………………..36 Air Filters………………………………………………………………………………………….37 Application………………………………………………………………………………………..37 Operating Practices……………………………………………………………………………...37 External Contamination…………………………………………………………………………37 Sampling Instructions……………………………………………………………………………..37 Section 7 --- Steps to Determine an Optimal Oil Change Interval……………………….39 Section 8 --- Sampling and Oil Change Schedules………………………………………...42 Section 9 --- Reference Glossary of Terms…………………………………………………………………………………44 Information Supplements…………………………………………………………………………45

Notice This publication provides guidance for determining the optimal oil change interval for Caterpillar Diesel engines with a 250 hour recommended interval according to the appropriate Operation and Maintenance Manual (OMM). Some models of Caterpillar diesel engines currently have 500 hour recommended oil change intervals. We suggest that the oil change interval for these engines not be extended beyond 500 hours unless Caterpillar Synthetic Diesel Engine Oil is used. Caterpillar offers a full synthetic diesel engine oil (Cat DEO 5W40), which may be used in any Caterpillar diesel engine. Specific oil change intervals have not been established for synthetic oil. Cat synthetic DEO 5W-40 performs better than mineral based oils in two areas:

- Synthetic oils have improved oxidation stability, especially at high operating temperatures. - Synthetic oils have improved flow at low temperatures, especially arctic conditions.

The increased ability of Caterpillar Synthetic Diesel Engine Oil to combat oxidation should permit oil change intervals longer than those recommended for conventional DEO. The oil analysis parameters contained in this publication pertain to oils with API classifications CG-4 or CH-4, however, the general procedure may be applied to diesel engines using Caterpillar Synthetic Diesel Engine Oil, except that use of FT-IR (Infrared Analysis) may be of less benefit. When using synthetic oil careful trending of the oil samples using Wear Rate Analysis is the most important factor in determining whether the oil has reached its optimal life. If the customer is not using Caterpillar Filters and Caterpillar Diesel Engine Oil, or is operating in severe applications, or using fuel with a high sulfur content, it may be necessary to reduce the interval from that recommended in the OMM. Natural Gas Engine Oils (NGEO) have well defined but significantly different formulations than either diesel or gasoline engine oils. However, NGEO’s are not regulated by API classification at this time. This means that oil suppliers can change their blending formulations, techniques, and base oil stocks at any time and without notice. Attempts made to optimize oil life on gas engines are thus complicated by potential variations in available NGEO’s. Therefore, for gas engines, we recommend that oil change intervals not be optimized using this procedure.

Section 1 – Why Manage Oil Change Intervals? Oil performance is a very significant factor in the life cycle of an engine, and ultimately impacts customer satisfaction with Caterpillar products. Any time a customer is considering oil change intervals that are different from those recommended for Caterpillar products, you should be involved. As a Cat Dealer, you should focus on helping customers manage the variables involved in optimizing oil change intervals. This guide supplements [Optimizing Oil Change Intervals – Diesel Engines (PEDP7035)], a customer-focused brochure, which emphasizes the need for dealer involvement in any program to establish new oil change intervals. The text from that bulletin is included as Section 2, of this guide. Please study this guide and the customer bulletin so you understand the entire process before beginning. Establishing optimal oil change intervals for engines in each particular application or machine model requires several months of careful monitoring with S•O•S fluid analysis. In the information that follow, we will refer to the process of optimizing oil change intervals as the “Project”. A balanced approach to lubrication management must be taken to ensure that costs are indeed minimized. Change oil too early and money may be wasted by throwing away some of the useful life of the lubricant, and from higher disposal costs. Change oil too late, and the risks of incurring even greater costs are increased through shortened engine life. The opportunity to optimize lubrication-related cost savings depends on a number of factors. Many of these factors can be monitored with S•O•S fluid analysis, allowing your customers to achieve balanced management of oil change intervals. Taking a Leadership Role As a Cat Dealer, you should take a leadership role in the Project to assure the process is well managed and the conclusions are appropriate. The success of the project depends on: • Understanding and adhering to the information and instructions in this guide. • Oil samples taken at the intervals outlined. • Complete and knowledgeable interpretation of data from each oil sample. • Adherence to drain intervals established during the Project. • Accurate records of hours on the engine, hours on the oil, make-up oil amounts and repairs. • Applying the newly established oil change intervals to engine in similar applications and/or machine

models. • Monitoring and recording fuel consumption, if possible, to assure a consistent load factor.

What Your Customer Must Do Carefully consider each customer who wants to extend oil change periods. To assure success the customer must have the following: • A capable person at the manager level to take ownership and oversees the project. • An understanding of the project time frame and requirements. • An excellent maintenance program including training, scheduling, and record keeping to assure that

samples are taken at the correct intervals. • Engines that are relatively new or recently overhauled ( less than one-third through anticipated life). • Engines that have been maintained at or below the oil change intervals published in the appropriate

Operation & Maintenance Manual, using an oil of the specified API performance and viscosity ratings.

• Engines that have a complete oil analysis history. • Machines that are used in a consistent manner, not moved into jobs of varying severity. • A commitment to use top quality oil and filters, preferably Caterpillar products. By far the most important customer requirement is a commitment to the effort and the control required for success. Don’t even begin until you are convinced the customer has demonstrated this commitment to you. Risk vs. Reward As with most business decisions, there must be consideration of the potential risks of extending engine oil change intervals along with the perceived rewards. The rewards include lower expense for oil, reduced maintenance labor expense and increased availability due to less time shut down for maintenance. But, these rewards can easily be offset by a slight decrease in engine life. Many customers expect 12,000 hours, or more, on an engine before overhaul. No customer wants to experience shorter engine life as a result of longer oil change intervals. Yet that is what can happen if the oil optimization Project is not carefully controlled. It is quite conceivable that extending oil change intervals from 250 to 400 hours could shorten engine life. Extending oil change intervals without a carefully controlled plan may result in shortened engine life, reduced productivity and increased operating costs. Please be certain that all parties involved in an oil optimization project are fully aware of the risks involved.

Potential Cost Savings vs. Risk The following formulae provide a very rough means of calculating the possible savings from extending oil change intervals past the recommended periods. The end result is to determine “break even point” in terms of engine life before overhaul. If the customer has a target engine life of 12,000 hours and intends to continue to achieve that life with extended drains, at what reduced engine life would he break even? In other words, at what point would the savings resulting from fewer oil changes be offset by reduced engine life?

Oil Change Interval Optimization Cost Savings Estimation

Factors: Current Overhaul Target Hours; Current and Proposed Oil Change Intervals; Costs for: Oil, Filters, Disposal of Oil/Filters, and Labor Required; Hourly Production Rate; Fleet Size. Calculation of Current and Proposed Oil Changes Current Overhaul Target Hours = Current Number of Oil Changes = “A” Current Oil Change Interval Current Overhaul Target Hours = Proposed Number of Oil Changes = “B” Proposed Oil Change Interval Calculation of Number of Oil Change Intervals Saved A – B = Reduction in Oil Changes = “C” Life Cycle Oil Change Interval Cost Savings C x Cost of Oil Change (oil, filter, labor) = Life Cycle Oil Change Savings per Engine Life Cycle Disposal Cost Savings C x Cost for Disposal of Oil and Filters = Life Cycle Disposal Savings per Engine Life Cycle Productivity Gain Savings C x Minutes per Oil Change = Production Hours Saved 60 Minutes Production Hours Saved X Hourly Production Rate = Life Cycle Production Gain per Engine Life Cycle Total Maintenance Savings: Oil Change Savings + Disposal Savings + Productivity Gains = Total Life Cycle Savings per

Engine

Oil Change Interval Gain/Risk Evaluation Calculations

Factors: Overhaul Cost (piston/ring/liner, valve guides/valves, main/rod/thrust/bearings), current overhaul target hour, total Life Cycle Savings per Engine (from calculations above). Current Life Cycle Cost Per Hour Calculation: Overhaul Cost = Current Overhaul Cost Per Hour Current Overhaul Target Hours Optimized Oil Change Interval Overhaul Breakeven Point [Overhaul Cost – Life Cycle Savings Per Engine] = Optimized Oil Change Interval Overhaul Current Overhaul Cost Per Hour Break Even Hours* * Using the new “optimized” oil change intervals, this is the minimum number of hours to overhaul required in order to “break even” in life cycle maintenance costs as calculated using the current overhaul cost per hour. Any hours gained above this break even point increases profit at the current overhaul cost per hour. Any hours less, or below this break even point increases costs at the current overhaul cost per hour.

Although these formulae provide a means of thinking about the risk/reward balance they actually may be skewed to the positive side of extending oil drains. This is because the formulae assume that the target hours will still actually be met using extended drains, and that no additional “scheduled repairs” will be required to meet the current target hours. This, in fact, may not be the case; engine life may be shortened. Additional formulae reflecting the reduced productivity and increased costs could be employed in an attempt to consider these factors, but these considerations are very conjectural and, therefore, may not be work the effort to compute. The Limitations of Oil Analysis Occasionally, oil analysis results will indicate no sign of problems while carbon and a varnish deposits are forming on the pistons. The first sign of a problem may be increased oil consumption as the result of stuck rings or bore polishing. Need to Inspect the “Iron” It is important that the optimization Project plan include removal and inspection of two or more power assemblies (piston, rings and cylinder liner) about half to two-thirds into the projected engine life. In other words, if the anticipated engine life is 12,000 hours, a piston inspection should be scheduled between 6,000 and 8,000 hours. A power assembly inspection should be done even if the oil analysis results indicate no sign of problems. The removed parts are to be visually inspected for signs of distress caused by oil degredation. Initial signs of ring sticking, excessive ring wear, liner polishing or liner scuffing would probably indicate that the engine will not achieve the overhaul life target with that particular oil and oil change interval. The piston should be inspected for varnish or carbon deposits under the piston crown and on the piston crown above the top ring land. Such deposits can cause piston overheating with resultant scuffing or piston cracking. Look for carbon build-up under the compression rings. Carbon under the rings can lead to ring sticking. The best reference for evaluating the deposits and wear is the Applied Failure Analysis reference book Piston, Ring & Liner Failures Analysis, SEBV0553. If abnormal wear or deposits are found on the parts removed from a engine which as been subjected to extended oil drains it is suggested that a piston pack from a similar model engine within the fleet which has been operated at the normal oil change interval be removed and inspected for comparison. This ability to compare the difference in engine condition is important. This is a good reason tohave a portion of the fleet remain at the standard oil change interval until the extended interval is verified as accepted.

It is important to discuss the possiblity of engine problems with the customer prior to starting the project. Problems or reduced engine life caused by extended oil change intervals are not the result of defective parts or workmanship and are, therefore, not warranty-related failures.

Section 2 – Optimizing Oil Change Intervals – Diesel Engines (Text from customer bulletin PEDP7035) Getting the most from your oil and your engine. Maintaining your engine oil is a very important factor in maximizing the productive life of your Cat engines and machines. It begins when you demand the higher standard of protection available from Cat engine oil and filters. And it continues as you work with your dealer to optimize the effective life of the oil. Cat engines have recommended oil change intervals developed through extensive testing and historical data. However, these intervals cannot take into account your specific operating conditions and other factors that my necessitate a different oil change schedule. S•O•S fluid analysis and other resources from your Cat Dealer help you understand the factors affecting your engine oil, so you can better manage your engines’ life cycles and reduce costs. Consider these factors when evaluating your oil performance To optimize oil change intervals, it is important to determine how well your oil will hold up under specific conditions. To do this, all factors affecting oil condition must be controlled and stabilized during evaluation. Everything that could have an impact on oil condition must be held constant during the evaluation period so you can monitor the effects of hours of use on the oil. Application – The same load should be applied (relatively the same amount of fuel consumed per hour) in the same operating and climatic conditions. Oil Filters – The same filters (preferably Cat filters) should be used for all engines in the test group, and they should all be changed at the same interval. Use Cat filters to guarantee you are using the highest quality filter available. Air Filters – Change only as indicated by the air filter service indicator. Use new, not washed or reclaimed filters, and use the same brand and type for all units in the test group. Again, use Cat air filters to assure high quality. Cooling System Maintenance – Cooling system problems contribute to more than 50% of all engine failures and problems. Initially, submit coolant samples for Level 2 S•O•S Coolant Analysis to assure the cooling systems on all test units are optimal. Assure that radiators are clean externally and internally. Proper coolant and conditioner levels should be maintained. Over-heating or over-cooling can increase oil oxidation and/or sulfur product formation. Use S•O•S Level 1 coolant analysis at each oil change to make sure your coolin gsystem and coolant are up to par. Operating Practices – Operating techniques impact how an oil responds and holds up to an application. Excessive lugging, excessive idling and full throttle on/off will all affect sooting and oxidation of oil.

Optimally Tuned Engines – Keep engines running according to specifications. Check boost, fuel settings, air/fuel ratio control and transmission shift points. Poorly tuned engines can lead to malfunctions or adversely affect operating temperatures, fuel consumption, or other parameters. External Contamination – Take a baseline oil sample from each engine in the test group at every oil change to make sure no external contaminants are introduced with new oil. Selection of Test Engines – Include engines with relatively low total operating hours and those never having grossly extended oil change intervals. Engines with higher hours have different wear and oil consumption rates than newer engines. Engines that have had grossly extended oil change intervals or that have used lower quality oils may already have irreversible oil-related problems at the start of the evaluation, i.e. lacquering, ring sticking and carbon build-up. Be sure to correctly and completely fill out the S•O•S sample bottle card or label. This information is critical to sample results and the interpretation process. In particular, it is essential to include the total hours (or odometer units) on the engine, the total hours/units on the oil, and the quantity of make-up oil added since the last oil change.

Provide complete S•O•S information

Variable factors affecting lubrication and wear There are a number of factors that operators and maintenance engineers can control to affect engine wear and costs. A general indication of how well a lubricant is performing during an oil change interval is the amount of wear metals generated during that time period. The rate and amount of wear occurring in an engine depends on four categories of causes (see chart, facing page). This chart provides a very simplified explanation of the causes of oil degradation and wear metal generation for diesel engines. The items shown in the “S•O•S Oi Analysis Test Results” column are those for which Caterpillar engineers have selected tests. 1. Maintenance Errors and omissions in routine preventive maintenance prictices, which affect oil

condition, result in increased engine wear. 2. Application Environmental and operational factors that contribute directly to increase wear

and/or oil condition degradation. 3. External Contamination Fuel, water, glycol or anything else getting into the engine lubricating

system from the outside, accelerating wear. 4. Internal Contamination The causes of excessive internal contamination are usually

misalignment of mating parts, improperly torqued bolts and nuts or defective parts. Internal contamination becomes a grinding agent which adds to internal debris produced by parts wearing together.

If S•O•S oil analysis indicates a problem in any of its tests, give consideration to each possible cause. Correct or alleviate the causes if possible. Be alert for changes in any of the Maintenance or Application factors which might lead to a problem. Doing this will help control and stabilize all the factors impacting oil conditions during the evaluation period. The oil change interval balance As with most business decisions, establishing an engine oil change interval beyond the manufacturer’s recommendation has both risks and rewards. Perhaps the biggest potential reward is increased productivity due to less maintenance downtime. But this productivity increase can be quickly eroded if recuded engine life causes repair downtime. Extending oil change intervals without a carefully planned an executed program is gambling with the life of your engines – and your cost of production. Your Caterpillar Dealer can help you establish optional oil change intervals with S•O•S fluid analysis service. Monitor oil consumption Not shown on the chart (previous page) is the addition of make-up oil. If make-up oil is added, all the oil analysis results will be affected. It is very important to keep close records an report the quantity added on each oil sample label.

Determining Optimal Oil Change Intervals We suggest you proceed beyond the manufacturer’s recommended oil change period cautiously in incremental steps of 50 hours. For example, first extend from the 250-hour recommended period to 300 hours. Stay with a 300-hour period for several changes and closely monitor the S•O•S results with samples taken as shown on the chart below. Four types of oil samples There are four common categories of oil samples involved in evaluating an oil change interval: 1. Samples of New Oil

A sample of the new oil is needed as a test reference to the used oil. The new oil sample must be the exact same oil as the used oil being tested. Any time a new shipment of oil is received, a sample of that oil must be submitted as the reference, even if it is the same brand, type and classification of the oil previously in use.

2. Baseline Samples After changing the oil and filter, run the engine until it reaches operating temperature and take a sample. This determines wear metal carryover from any oil left in the pan from the previous interval. It also reveals if any external contaminants were introduced through the oil fill process. During the evaluation period, take a baseline sample after every oil change.

3. Samples at Shortened Intervals Taking samples at less than the recommended oil change interval is essential to monitoring the oil degradation process. This practice will allow you to determine the rate of oil additive package depletion, wear accumulation and any external contamination entry. You must establish these rates for the recommended oil change interval before you begin an extended interval evaluation (see chart).

4. Samples at Oil Change Test results from the samples taken at the time of each oil chagne will indicate the final levels of oil degradation and wear accumulation. These results, along with the shortened interval sample results, will be evaluated to establish the optimal oil change interval for your engine. Once the optimal interval has been established, submit a sample at half that interval and, of course, at each oil change.

Engine coolant samples Because many engine problems are influenced by the cooling system, coolant samples should also be submitted. Level 2 Coolant Analysis should be performed at the beginning of the project and at 1,000 hour increments. Do a Level 1 test at the other oil changes during the project.

Work with our experts We will work with you to optimize the oil change periods for your Cat engines. Keep in mind, however, that the process of determining new oil change intervals is not simple. It requires that you work closely with our staff over a period of several months. Once new intervals are established, it will be more important than ever to carefully monitor oil performance and engine wear – using S•O•S analysis for both oil and coolant – to make sure there aren’t any problems. Use Cat Oil and Filters – If you want to evaluate the possibility of oil change intervals other than those published by Caterpillar for your engines, you must protect your engine with high-quality products. Cat filters are designed to do the job beyond the published oil change periods. This extra protection assures you can maintain the same filter change periods as your newly established oil change periods. Although there may be a small difference in price, it is well worth it to guarantee that your engines are protected by the best oil and filters. And Use Cat Diesel Engine Oil – or a premium quality API CG-4 or CH-4 oil. Diesel engine oils which meet API specifications CG-4 and CH-4 contain the best additive package and base oil stock to help you achieve longer oil use and maximum engine life. But even within those API categories there are wide variations in quality (which is reflected by the range of prices for CG-4 and CH-4 oil). Oil is viewed by some as a commodity, but as a rule, you get what you pay for – a higher quality add pack and base stock costs more than lower quality alternatives. To ensure you get the best oil for your money use Cat oil in your engines.* Extend equipment life with quality Cat maintenance products Cat Fluids: Formulated to provide high standards in performance and life. Cat Fluid Filters: System engineered for optimal performance and protection. S••••O••••S Analysis: The ultimate detection and diagnostic tool for your equipment. Maintenance Software: Trend Analysis Module (TAM) for S•O•S results. Maintenance Control System (MCS) for scheduling and record keeping and Preventive Maintenance Planner (PMP) for comprehensive maintenance checklists.

Section 3 – Optimizing Oil Change Intervals – Diesel Engines Following is a brief description of the procedure you should follow in assisting your customer with an engine oil optimization project. The rest of this bulletin contains details of the procedures required. Please read and understand all of this material before initiating the Project. Also, be certain your customer understands the extent of the Project and agrees to work closely with you. The following S•O•S tests are required for the Project.

- Wear Rate Analysis – spectrometric analysis (ICP, DCP, or AA) - FT-IR -- for Oxidation, Sulfation, Soot, and Nitration and scan for possible contamination

by Water, Glycol or Fuel. - Fluid Contamination Tests – for Water, Glycol or Fuel as dictated by FT-IR scan. - Total Base Number (TBN) -- preferably by titration (ASTM Test D2896), alternatively by

Dexil Kit. The following are optional tests which should be performed if possible:

- Total Acid Number (TAN) – preferably by titration (ASTM Test D664), alternatively by Dexil Kit.

- Kinematic Viscosity - ASTM Test D445. Project Procedure 1. Obtain a new oil sample A new oil sample is required as a reference for FT-IR Oil Condition Analysis. Obtain a new reference sample from every shipment of oil your customer receives. These samples can also alert you to the possibility of a contaminated new oil source. 2. Take a baseline sample A baseline oil sample is to be taken after changing the oil and filter and running the engine about 15 minutes. Note the amount of wear metal carryover as a reference for the following samples. A baseline coolant sample for Level 2 Analysis should also be taken at the initiation of the project. 3. Take samples at 75, 150 and 250 hours of operation* These provide oil degradation and wear metal generation rates during the standard 250 hour oil change interval. This will provide a basis for future comparisons. If a sample reveals contamination by fuel, water, glycol or dirt, investigate and correct the cause before proceeding. 4. Determine if the oil is fit for further use. If the wear metal generation rates and oil condition factors appear to be satifactory after two or three oil changes, extend the oil change interval by 50 hours and repeat the sampling procedures at 250 and 300 hours. *Remember, oil change optimization does not always mean extension beyond the recommended interval. If the oil condition is beyond the parameters and/or if the wear metals are significantly higher at 250 hours than they were at 150 hours, excessive internal wear has already occurred. Change the oil and filter, then repeat the procedure (baseline sample and

samples at 75, 150 and 250 hours) to determine if the same wear rate occurs. If it does, you should reduce the oil change interval by 50 hour increments until a satisfactory oil change interval is determined. Work closely with the customer to achieve an oil change interval that optimizes engine life. Failure to achieve a 250 hour oil change interval rarely occurs if a top quality CH-4 or CG-4 oil is being used. If the oil break point is less than 250 hours suggest that the customer use a higher quality product, preferably Caterpillar diesel engine oil. 5. Closely monitor oil condition and wear rates As you extend beyond 250 hours, carefully observe the results of each sample for a break point at which the oil condition parameters are exceeded and/or wear rates markedly increase. This is the break point for the oil. When the break point is determined, the oil change interval should be reduced by 50 hours from that sample interval. Operating an engine beyond the break point during successive oil changes will result in a build-up of lacquer, varnish and carbon on critical parts and reduce engine life. 6. Record all important maintenance information Keep a chronological history of all inspection reports, engine adjustments, maintenance and repairs performed during the Project. Also keep a record of oil and fuel consumption. These records are important in determining which of the variables may have had an impact on the engine oil’s performance. If a good record keeping system is not already in place, consider using the Caterpillar Maintenance Control System (MCS) software: Medial No. JERC4300 in Windows 95 and Windows NT. The Media Number to upgrade the former DOS version of MCS to the Windows version is JERC4301. Both wear rates and oil condition (e.g. oxidation, sulfation and soot) MUST be factored into the oil analysis results to account for make-up oil. A significant increase in oil consumption can cause wear metal concentration in ppm as well as oxidation and soot levels to decrease. If oil addition is not considered it may appear that an engine is operating with no problems when it may actually have already suffered bore polishing and other damage. Note: This procedure applies to engines with 250 hour recommended oil change intervals. We suggest

that the engine with a recommended 500 hour oil change intervals not be considered for an extension beyond that point. In fact, we suggest you carefully monitor these engines to assure that the oil is protecting them up to the 500 hour point. In some instances, it has been necessary to reduce the interval from 500 hours, especially if an oil other than Caterpillar diesel engine oil is used.

Section 4 – Factors Affecting Oil Performance and Engine Wear Any good lubrication management program must maintain oil change intervals so the engine receives maximum and continual protection. If oil degrades to the point where protection is diminished, engine life cycle is shortened and costs begin to rise. A number of factors can contribute to oil degradation and accelerated wear. They can be placed into two categories: fixed factors and variable factors. Fixed Factors By establishing an oil change optimization program, you and your customer have already identified two fixed factors. 1. You will be testing a specific engine design. And, 2. You will be using one particular oil. So for the purposes of this project, the engine design and brand/type of oil can be considered fixed. The interaction of these two fixed factors, together with certain variables, will determine the optimal oil change interval. Engine Design An engine’s design and operating characteristics dictate the need for certain oil lubircation qualities. Temperatures, cylinder pressures, horsepower, type of aspiration (naturally aspirated, turbocharged or turbocharges/aftercooled), overall performance rating, sump capacity, oil consumption rate and fuel consumption rate are some of the engine design parameters that impact a lubricant’s useful life. When developing a new engine model, manufacturers consider the lubricating capability of the oil as if it were another engine part. As a result, engine features play a significant role in determining the manufacturer’s recommendations for lubricant classification, viscosity ranges and oil change intervals. The useful life of the same oil used in two or more differently designed engine sin the same application will vary due to engine design and operating characteristics. Please note that two different Caterpillar engine models in the same application may, therefore, have different optimal oil change intervals. Engine oil technology of the past will not provide optimum life and performance in current and future engines. Caterpillar engines have advance through the years to provide the performance and features that customers demand. These advancements have resulted in numerous improvements: ! Increased horsepower, from smaller sized engines. ! Smokeless combustion ! Reduced emissions ! Reduced fuel consumption ! Reduced oil consumption

! Better response and lugging ability with electronic engine controls All these engine improvements have an effect on the engine oil. Increased horsepower drives up temperatures and promotes oil oxidation. Emissions reductions increase soot levels in the oil. Concurrent with higher demands on crankcase oil, engine users are pressing for longer oil drain intervals. Oil technology must keep pace with engine technology and customer needs to provide products that work together for optimum engine life and performance. Engine oil has undergone changes to meet the increasing demands on engines for emissions and performance. These changes are best tracked by the American Petroleum Institute (API) service category and the corresponding engine improvements. API and Caterpillar PC Engines Caterpillar has been active in development of diesel engine oils (DEO) since the 1930s, and Caterpillar set the standards for DEO until the early 1970s. In 1973, API introduced their oil classification system. API CD (previously called Caterpillar Series 3), was adequate for Caterpillar precombustion chamber (PC) type diesel engines. By the early 1980s, the drive was on for improved fuel economy and diesel engines were changing. New engine designs were introduced with direct injection (DI) fuel systems. In 1983, API introduced the CE oil category to address the needs of both DI and PC diesel engines. API and Caterpillar DI Engines The CF-4 category was introduced in 1990 as the first oil category totally dedicated to the modern direct injection (DI) diesel engine. Low emissions, reduced fuel consumption, and higher power ratings were all driving the designs for diesel engines. CF-4 oils tightened the limits on piston deposits to improve engine durability and reliability. By 1994, the emissions laws has changed again and low sulfur diesel fuel was common in North America. Responding to these changes, the API released CG-4 in 1995, and CH-4 in 1998. These oils are designed to operate in the latest low emissions DI diesel engine and in non-regulated DI diesel engines. CG-4 and CH-4 are especially effective in controlling soot and wear. The following chart shows the progression of oil categories and engine performance. For up-to-date lubrication performance recommendations, refer to the Operation and Maintenance Manual Supplements listed on page 46 of this bulletin. Note: Some oil formulations in particular engine applications will form more deposits than others on engine parts over time. This starts to happen as the oil nears its breakpoint. With some oils, it takes only a few times of operation near the breakpoint for lacquering and carbon to build up enough to cause ring packing and cause an increase in oil consumption. The absence of any apparent or significant increase in wear metals (particularly iron) as the oil change period is being “walked out” in time does not necessarily mean that all is proceeding well. To the contrary, it can mean damage is occurring. Therefore, be sure to monitor the key wear metals for moderate increases normally expected to accumulate because of the increase hours on th eoil. If the wear metals (especially iron) do NOT increase accordingly something is wrong…especially if iron decreases. In this case, more than likely, the wear metals are being diluted by an increased amount of

make-up during the oil change interval. If so, ring packing and/or bore polishing has probably already occurred. Variable Factors The amount of wear occurring during an oil change interval is a general indication of how well a lubricant has performed during that time period. There are several variable factors that operators and maintenance engineers can control to affect a lubricant’s performance. The rate and amount of wear occurring in an engine depends on four factors, as discussed in customer bulletin PEGP7035 (Section 2). These variables are: ! Maintenance ! Application ! External Contamination ! Internal Contamination All of these variables affect the overall condition of the oil. Oil Condition is monitored by S•O•S oil analysis. Most CH-4 and CG-4 oils will do a satisfactory job of controlling engine wear in their early hours of usage. Engine damage and wear becomes a problem when the oil begins to deteriorate. Deterioration begins at early hours for a low quality oil and at considerably higher hours for top grade oils. However, any oil will eventually deteriorate and begin to allow engine damage and wear. In general, the objective of an oil change optimization program is to identify the usage interval at which a particular oil no longer provides sufficient protection for the engine components. The variable affecting engine oil performance are discussed in detail in the next section.

Section 5 – Variable Factors Defined Managing Oil Change Intervals Managing oil change intervals is a matter of monitoring the oil condition and the corresponding change in wear metal levels and rates of generation. Assuming there are no external or internal contamination problems, there are only two factors remaining (maintenance and application) that could adversely affect oil condition and, thereby, reduce engine life. An important consideration during the Project is to hold all factors as constant as possible with the exception of one: the oil change interval. Varying the oil change interval will alter the oil condition, which in turn will affect the overall rate of wear metal debris generation. It is this inter-relationship between the length of time an oil has been in use and the rate of wear metal debris generation that determines the optimal oil change interval. A significant increase in the rate of wear metals in the oil marks the point where the oil has begun to lose its lubricating properties. We call this the oil’s “break point.” Trending infrared analysis results (oxidation, soot, sulfation and nitration levels) and trending the wear metals (with consideration for make-up oil) will be of primary importance. The goal is to avoid exceeding an oxidation, soot or sulfation level that results in an increase in wear metals. During the Project, the oil’s break point will be determined. Reduce the oil change interval 50 hours from the oil condition break point. This new interval – defined by infrared and wear metal trend increases – will be the optimum oil change interval for the specific oil in use, for that specific engine, in that specific application. Ultimately, your goal is to establish an oil change interval that is based on an increase in Oil Condition Analysis (infrared) trends before the wear metal trend increases. If the oil change is delayed each time until the wear metal increase indicates oil degradation, unacceptable engine wear will have already occurred. If this happens repeatedly, the life of the engine will be shortened. So it is important to establish the optimal change interval at the point before the oil has deteriorated. If any variable changes, a new optimum oil change interval must be determined. Discussion of Variable Factors Maintenance 1. Oil Type – Engine manufacturers recommend a classification and viscosity of oil based on an

engine’s performance and operating requirements. Not all oils of the same classification (CH-4, CG-4 for example) are of the same quality. In fact,

there is a range of quality within a given classification. The API classification only defines the minimum performance standards that an oil must meet.

The key to optimum engine life is the consistent use of the best quality oil in that classification and viscosity. Using incorrect API classifications, viscosities, TBN levels or poor quality oils will result in shortened engine life.

In a genuine attempt to keep maintenance costs down, oil is sometimes purchased based on price

within a classification rating. But like everything else, you get what you pay for. Generally, the higher priced oils will perform better than the lower priced oils of the same classification rating, providing more protection over time than the lower cost oils. Therefore, it is imperative that the best quality, classification, viscosity and TBN oil be used starting with initial fill.

2. Plugged Air Filters – Restricted air flow affects the ratio of air to fuel entering the combustion

chamber. An imbalance in this ratio impacts sooting. A decrease in air flow results in a relative increase in fuel. This produces still more soot. Left uncorrected, this condition can accelerate wear.

3. Engine Fuel System Settings – An out-of-tune engine can contribute to hgiher operating

temperatures, improper air-to-fuel ratio and oil degradation. 4. Extended Oil Changes – The longer an oil is in use and the more it is exposed to air, heat,

combustion products, contamination and moisture, the more it will degrade due to oxidation, nitration, soot and sulfation. All other factors being equal, different oils degrade at different rates. Engine manufacturers recommend oil change intervals based on their research and knowledge of engine design and available oil classification performance capabilities.

The optimal life of the oil filter should also be taken into account. When extending oil change intervals, Cat Filters are strongly recommended for their superior construction and strength. They have been proven to achieve a 500 hour oil change interval.

5. Cooling System – The cooling system must be properly maintained for optimum engine operating temperatures. High temperatures increase the rate of oil oxidation.

Coolant that remains below optimum temperature causes more moisture to condense within the crankcase, and increases acid formation in the oil. Acid formation depletes the TBN buffers more rapidly, resulting in metal attack.

6. Fuel Sulfur – A final factor to consider is the sulfur level of the fuel. Caterpillar recommends that fuel sulfur not exceed 0.5% by weight. This is not a problem in North America because of government mandates that sulfur in on-highway #2 diesel fuel not exceed 0.05% to help control exhaust particulate emissions. This low sulfur fuel is also widely used in the off-highway market. Off-highway diesel fuel in North America is mandated to not exceed 0.5% fuel sulfur. Most countries have a limit of 0.5% for all diesel fuel. However, diesel fuels in some locations may legally be sold with sulfur content up to 1.0%. In some places, the level may even exceed 1.0%. If you are uncertain of the sulfur level of the fuel being used, be certain to ask the fuel supplier to provide that information for each shipment of fuel. Suppliers are required to provide fuel sulfur information upon request. If the sulfur level exceeds 0.5%, oil change intervals should not be

increased beyond those published and, in fact, many need to be shortened. For more information about fuel sulfur and an oil’s TBN requirements, please refer to Oil In Your Engine (SEBD0640).

Application

1. Geographic Location/Climate – Ambient temperature, elevation, humidity and dust all combine to affect oil degradation rates. Temperature extremes can either incrase oxidation (heat) or contribute to the formation of acids (cold). Engines operating at higher elevations experience accelerated sooting as if they were operating with partially plugged air filters. High humidity is a factor in the formation of acids (sulfation), particularly in combination with cool temperatures. Dust acts as a grinding agent on mating surfaces, accelerating the build-up of wear particles in the oil.

Note that oil condition factors and, as a consequence, the rate of wear metal generation may vary from summer to winter, or from the wet season to dry season. One seasonal factor is repeated “cold starts” in cold climates. Another cold season factor is the use of ether as a starting acid. Both will increase wear of the piston, rings and cylinder linders.

In conditions such as these, the expertise and experience of the Cat Dealer’s S•O•S interpretation plays a major role in the success of Project.

2. Operating Procedures – Engine operating extremes over long periods will increase the rate of oil

degradation. Such extremes include lugging, long idling periods, rapid acceleration and varying load factors.

3. Severe/Improper Operation – Severe operation causes higher than normal loading on critical

engine components. Excessive heat can build up, contributing to oil degradation (oxidation). Heat spikes add to the thermal stressing of critical engine components. This increases the chances of cracks, resulting in coolant leaks into the oil.

4. High Operating Temperatures – High temperatures cause both the oil and the oil additives to

oxidize. The end result is a loss in lubricating properties and an increase in viscosity. Performance can be affected by resins and lacquer that form as a result of oxidation on pistons, ring grooves, connecting rods, and turbocharger shaft. The rate and degree of oxidation depends on engine operating temperature, cooling system performance and the length of time the oil is in use.

Oil Condition As a crankcase oil experiences the various Maintenance and Application aspects discussed above, it eventually begins to lose it ability to adequately lubricate and protect engine parts from wear and damage. The S•O•S program quantifies this oil deterioration by comparing certain qualities of the used oil sample to the level of those same qualities the oil possessed when new. As a general term, we call these declines a reduction in “Oil Condition.” In particular, S•O•S oil analysis quantifies:

! Oxidation ! Sulfation and TBN ! Soot ! Viscosity 1. Oxidation – Oil oxidation occurs when oxygen molecules in the crankcase air combine with the

oil and certain additives in the oil. Most people understand rusting, which is what happens when iron and oxygen are in contact. Oil oxidation is similar, resulting in a chemical change in the oil’s formulation. As oil oxidizes, it loses its lubricating qualities due to reduction of additive strength, increases in viscosity and the formation of resins which adhere to engine parts.

The longer an oil is in use, the more the anti-oxidant additive package is depleted. Oxidation is accelerated by high temperatures. Ethylene glycol and water contamination, copper from oil cooler tubes or other components, and acids from fuel sulfur will also increase the oxidation rate and reduce the oil’s lubricity. The end result of oil oxidation is oil thickening, resin formation, piston deposits, a loss of lubricating properties and accelerated wear. Once the anti-oxidant additives are depleted, oxidation progresses at a rapid pace. For this reason it is important to sample the oil at 50 hour intervals once past the 250 hour recommended change period. While all contaminants are harmful to engines, the chemical action of oxidation is one of the most harmful. It has been observed that as any diesel oil’s oxidation level approaches .15 ABS/cm (absorbance unites per cm) (50% allowable) as determined by infrared analysis procedures consistent with Caterpillar guidelines, the rate of wear metal generation (particularly iron) increases. A significant increase in wear metal generation in conjunction with oxidation levels at .15 ABS/cm and above should be initially interpreted as the break point of the oil. The oil should be changed and closely monitored two additional intervals to determine if the trend repeats. If it does (and no other factors have changed), the break point relative to oxidation level has been identified. The oil change period should be reduced by 50 hours from the time (in hours on oil) where the oxidation level increase caused a corresponding increase in the wear level rate. Please remember than in any case, there is an absolute limitation for oxidation. For all Caterpillar engines, in any application, using any brand of oil, oxidation should not be allowed to go above .30 ABS/cm (100% allowable) as determined by infrared analysis. Oil oxidation occurs in all diesel engines, as well as natural gal engines, transmissions and hydraulic systems.

Effects of Oxidation

! Reduction of oil’s lubricating properties ! Piston deposit formation, sticking rings, broken rings ! Increase in oil viscosity ! Oil filter deposits and blockage Benefits of Determining Oxidation

! Helps determine an oil’s anti-oxidation capability/capacity ! Indicates high temperature operation and/or extended oil change periods ! Enables good management of oil change intervals when used in conjunction with wear metal

analysis and other infrared tests ! May indicate a cooling system problem Probable Causes of Oxidation ! Oil drain intervals exceed the oil’s ability to control oxidation ! High temperature operation caused by defective or incorrectly maintained cooling systems and/or

excessive load (lugging) conditions ! Contamination such as ethylene glycol, water, copper and acids caused by fuel sulfur ! Shutting down a hot engine rather than allowing it to cool down first 2. Soot – Soot is a by-product of the combustion process. It is made up of carbon from partially

burned fuel and inorganic ash left from the burning of additives in the oil. Soot is produced by all diesel engines, but engine design is a factor in determining how much soot is produced, how much is eliminated through exhaust and how much is collected in the oil. The relationship of volume of fuel burned to sump capacity, the oil’s dispensancy ability and the oil make-up rate determines an engine’s capacity for handling soot. In fact, the rate of soot production in an engine is a function of engine design, oil consumption, fuel quality and fuel consumption. However, the lubricating oil API classification and the quality of the oil (base stock and additive package) provided by the producer are the most significant factors in determining how much soot can collect in an engine’s sump before damage occurs.

All engine oils contain dispersants that keep soot particles in suspension and keep them from sticking together. But when the additives are depleted, soot particles start to stick together and form larger particles. When this occur, wear accelerates. Engineers are not certain how soot causes wear. Whatever the reason, excess soot contributes to wear. Oil classification and performance characteristics play a key role in controlling soot. Current CH-4 or CG-4 oils have higher dispersant additive packages to meet the higher levels of oil sooting resulting from very strict U.S. and worldwide exhaust emission regulations. This is not to say that current engine designs produce more soot than those of the past. On the contrary, today’s engines are designed to minimize soot. Environmental regulations prevent all of the soot from being exhausted into the atmosphere. As a result, the ratio of soot being collected in the oil rather than exhausted out the stack has increased. However, higher soot readings may not necessarily point to increased engine wear. Soot kept in suspension by superior lubricant additives does not cause accelerated wear. The problem occurs when the oil’s dispersant additives degrade over time, allowing soot particles to agglomerate. Today’s oil formulations, notably the CG-4 and CH-4 classifications, have significantly increased the capacity to keep soot particles in suspension. However, there are different quality levels of oil available within a classification. When top quality CG-4 or CH-4 oils are used, it is not uncommon to see soot levels in the 150% allowable (and above) range with no corresponding increase in wear metal. Any oil should be evaluated on a case-by-case basis because of potential performance differences within these oil classifications. Also keep in mind that an oil’s classification is a minimum performance rating

classification. Premium grade oils, like Cat Diesel Engine Oil, exceed these minimum standards. In fact, Cat DEO has the most superior oil additive package of any CG-4 or CH-4 oil. It is important for customers to understand that a superior lubricant, such as Cat CH-4 or CG-4 does not reduce the amount of soot produced by the engine, but keeps the soot particles dispersed thereby reducing engine wear, sludge deposits and oil filter plugging. In fact, a higher quality oil will indicate a higher level of soot in oil analysis samples than a lesser quality oil with lesser quality soot dispensancy package. Effects of Soot ! Agglomerated soot can absorb and diminish a portion of the oil’s additive package ! Wear accelerates when soot particles agglomerate (stick together) ! Contribute to oil viscosity increase ! Decrease the lubricating properties of the oil ! Contributes to piston deposits and ring sticking ! Plugs filters after dispersant depletion Benefits of Determining Soot ! Contributes to management of oil change periods when used in conjunction with other infrared

testing (oxidation, sulfation), wear metal results (lead, aluminum, iron, chromium), and viscosity readings

! Provides an indication of engine performance problems ! Provides an indirect indication of a change in load factor Causes of Soot ! Improper engine operation; i.e., rapid acceleration and deceleration, excessive lugging, long periods

of idling ! Incorrect air/fuel ratio ! Clogged or restricted air filter ! Turbocharger problems ! Incorrect fuel setting ! Incorrect timing ! Fuel nozzle problems ! Crankcase blowby ! Restricted exhaust ! Fuels with higher distillation end points ! High altitude operation 3. Sulfation – Sulfur compounds are by-products of combustion. Sulfur oxides formed when

sulfur-containing diesel fuels are burned may combine with water to form acids. A number of factors determine the potential damage from acid formation.

! The amount of sulfur in the fuel ! The amount of fuel burned during the oil change interval ! The acid-neutralizing additive package of the oil

! Sump capacity ! Oil consumption rate ! Length of oil change interval ! Engine operating temperature ! Ambient air temperature ! Humidity All diesel fuels contain some sulfur. How much depends on the amount of sulfur in the crude oil and/or the refiner’s ability or desire to remove it. One of the functions of lubricating oil is to neutralize sulfur by-products (sulfurous and sulfuric acids), as well as organic acids formed by oxidation. In this way, the oil helps prevent corrosive damage. Additives in the oil contain alkaline compounds formulated to neutralize these acids. The measure of reserve alkalinity in the oil is known as the Total Base Number (TBN). Generally, the higher the TBN value, the more reserve alkalinity capacity the oil contains. Sulfuric and other acids signal danger to metal engine parts, causing corrosive wear to the surfaces of valve guides, piston rings and liners. The type of corrosive wear attributed to high sulfur content fuel can also accelerate oil consumption. Because the level of sulfur oxides in a used oil increases with a longer oil change interval, checking the TBN of oil is important. The TBN of the oil should be checked for each oil sample. Engine jacket water outlet temperature influences the formation of corrosive acids. Even when using a fuel with less than 0.5% sulfur coolant temperatures below 79ºC (175ºF) can cause acid vapors to condense in the engine oil system and corrosive attack occurs. Low temperatures also increase the amount of water condensation which otherwise might have evaporated out of the oil at normal operating temperature. This residual water depletes certain oil additives and reduces the oil’s ability to protect engine parts. This can cause deposits, sludge formation, lacquering, varnish and carboning. In applications where humidity is high, acids are more likely to form because of the additional water in the air. So, both low coolant temperature and high humidity can result in increased corrosive attack. It has been observed that as an oil approaches a sulfation level of .24 ABS/cm (80% allowable), as determined by infrared analysis procedures consistent with Caterpillar guidelines, there is a corresponding significant increase in wear metals, especially iron. Initially, this should be interpreted as the break point of the oil. The oil should be changed and closely monitored for two additional intervals to determine if the trend repeats. If it does, the break point relative to sulfation level has been identified. The oil change period should be reduced by 50 hours from the time (in hours on oil) where the sulfation level increase caused a corresponding increase in the wear level rate. Oil should be changed as the sulfation level causes a significant trend increase, when sulfation reaches 100% allowable and/or when the TBN value of the oil reaches half the TBN value of the oil when new. Reference “Oil and Your Engine”, SEBD0640 for more detailed information. Effects of Sulfation ! Corrosive attacks on the metal surfaces of valve guides, piston rings and liners ! Contributes to ring sticking

Benefits of Determining Sulfation ! Monitors the effect of sulfation on the engine ! Indirectly monitors the fuel quality (sulfur content) ! Indicates fuel consumption and engine load ! Indirectly indicates cooling system problems (running too cool) Causes of Sulfur Product Formation ! Low TBN relative to fuel sulfur level ! High sulfur content of the fuel ! Cool operating temperatures ! High humidity ! Water in the crankcase (condensation and other sources) ! Excessive crankcase blowby 4. Nitration – Nitration is a by-product of combustion. It occurs when nitrogen and oxygen in the

air combine at high temperatures and pressures in an engine’s combustion chamber, forming nitrogen oxides (NO2). As the nitrogen is oxidized to NO2, nitrous and nitric acids are formed. As oil is thrown onto the cylinder walls and then wiped down by the rings, NO2 compounds are washed into the crankcase. These acids react with the oil’s TBN, oxidizing the oil and its additives. While Nitration occurs in all type of engines, it is of particular concern for natural gas and other spark ignited engines.

Effects of Nitration ! Reduction of oil’s lubricating properties ! Increase in oil viscosity ! Deposit formation ! Corrosive wear ! Oil filter plugging Benefits of Determining Nitration ! Helps determine an oil’s anti-nitration capability/capacity ! Provides an indication of low (or high) temperature operation, and/or extended oil change periods. ! Enables good management of natural gas engine oil change intervals when used in conjuction with

wear metal analysis and other infrared tests ! May indicate a cooling system problem Probable Causes of Nitration ! Oil drain intervals extended beyond the oil’s ability to control nitration ! Low temperature operation caused by defective or incorrectly maintained cooling systems and/or

light load conditions ! Incorrect spark timing (natural gas engines)

! Improper air/fuel ratio ! High humidity ! Crankcase blowby 5. Viscosity – Viscosity is defined as a measure of a fluid’s resistance to flow. The standard

measure of this property for crankcase oils is termed “kinematic viscosity.” Kinematic viscosity is based on the ability of an oil to flow under the influence of gravity through a capillary tube. The test for kinematic viscosity is defined by ASTM D445.

The Stoke is the unit of measurement for kinematic viscosity. For purposes of engine oil classification the Stoke is an inconveniently large unit of measurement. Therefore, a smaller unit, the centistoke (cSt), is used to define the viscosity of crankcase oils. To qualify multigrade crankcase oils, the ISO has specified that ASTM D445 be performed on multigrade crankcase oils at 40ºC and 100ºC. The ISO Grade determined by performing ASTM D445 at 40ºC is given a suffix “W”. The ISO Grade determine at 100ºC has no suffix. Crankcase oils used in modern direct injection diesel engines are multigrade, injection diesel engines are multigrade, meaning they meet a specific centistoke requirement at both 40ºC and another requirement at 100ºC. Therefore, the resultant ISO ratings for crankcase oils appear in a format as follows: 10W-30, 15W-40, or even 20W-20. Multigrade mineral oils are created by starting with a light grade base stock oil (one which meets the “W” requirement) and blending into it certain long chain polymers called “viscosity improvers” which cause the oil to perform at the required viscosity grade specification at the higher (100ºC) temperature test, as well. A three centistoke viscosity increase or decrease from the new oil’s viscosity is the condemning limit for crankcase oils during use. Crankcase oil may begin to lose its lubricating properties after experiencing a 3 cSt. Change. An oil which has experienced a viscosity change of the magnitude should not be continued in use because damage to the engine may occur. There are two most frequent causes for an increase in crankcase oil viscosity. The first is an accumulation of combustion by-products (mainly soot) which can thicken the oil. The second is heat, which can cause oxidation. Also, oxidation, with resultant oil thickening, can occur if engine coolant (glycol) enters the crankcase. Water from condensation or contamination can also contribute to oxidation. Additionally, molecular copper which can leach from oil cooler cores, can act as a catalyst causing accelerated oxidation. There are two primary reasons an oil might experience a decrease in viscosity. The first is fuel dilution, which is not a failure of the oil but a contamination problem which must be promptly resolved. Another possible reason for a viscosity decreases is shearing of the long-chain polymer molecules which comprise the viscosity improver additives. In such an instance, the oil can no longer maintain performance at higher temperatures and migrates towards the lower viscosity of the base stock mineral oil. The time it takes for an oil to lose viscosity due to “shearing” is dependent upon the quality of the oil’s base stock and additive package, and the severity of the engine application. In either case, fuel

dilution or shearing, the oil can “thin down” to the point it can no longer maintain good performance at operating temperatures. When investigating a change in oil viscosity be alert to the possibility that the wrong oil was used during an oil change or as make-up oil. Careful analysis of FT-IR test results can help determine this possibility. An oil which has experienced a three centistoke change has been used beyond its useful life. An increase in wear metal debris will probably be detected in samples of oil which have experienced this amount of viscosity change. Oil Condition Summary In general, the effects of oil degradation are carboning of piston crown areas, ring grove packing with resultant ring stocking, liner bore polishing, and lacquering of connecting rod pin areas and piston undercrown. The oil degradation results may first be noticed as an increase in iron ppm accompanied by an increase in oil consumption. If wear metal concentrations are not adjusted to consider the increasing quantity of make-up oil break point of the oil can easily be missed. External Contamination External contamination is any undesirable matter that gets into the engine. Following is a list of external contaminants and their potential impact on engine wear and performance. 1. Milling and Repair Debris – Every engine manufacturer takes steps to assure that engines are

clean when they leave the factory. However, some minute factory machining debris might get caught in internal crevices and later work their way loose. If an engine has recently undergone an overhaul or other major repair, changes are that repair debris has been introduced into the lubrication system. Baseline oil samples are important in controlling damage from debris introduced during manufacturing or repair. A baseline oil sample should be taken after the first 15 minutes of operation to determine initial wear elements.

2. Solvents/Sealants/Greases – Some remnants of solvents, sealants or greases may remain inside

the engine. Many times these external contaminants will show up in the oil sample test results as high readings for molybdenum (grease), lead (grease), silicon (solvent, sealant) or copper (anti-seize or sealant). Depending on the amount of foreign substance left in the engine, these may or may not be harmful to the engine components. In any case, once a foreign substance has been detected, it is important to change the oil and filter immediately to rid the system of the contamination. Taking a baseline sample approximately 15 minutes after the change will provide a determination of how much this contamination was reduced.

3. Lacquering – Lacquering is an end product of the oil oxidation process caused by heat and other

oxidizing catalysts. Lacquering causes ring sticking, connecting rod pin sticking, under-crown deposits and accelerated piston, ring and liner wear. No oil analysis test is available to directly measure the amount of lacquering that has occurred in an engine. However, an engine’s

oxidation trend is an indirect indicator. If oxidation has repeatedly been high, it’s likely that increased lacquering has occurred.

4. Agglomerated Soot – Soot becomes a contaminant when the oil’s dispersant additive can no

longer hold soot particles in suspension, allowing them to stick together (agglomerate) and form larger particles. As some degree in engines. Keep in mind that soot only increase wear when it is not longer controlled by the dispersant additives.

5. Water and Coolant – Corroded liners, leaky had gaskets, head cracks and water pump leaks can

allow water into the engine crankcase. This coolant contamination can vary from minute amounts to large quantities. An oil sample may or may not test positive for water, depending on the volume that entered the engine. If the leak is small, the heat of engine operation may evaporate the water, leaving traces of sodium (ELC or DEAC) and potassium (ELC). In more severe cases (more than .5%), water can cause the oil to emulsify and greatly reduce its lubricating and protection properties. Ultimately, it can form sludge, block oil passages and clog filters. In the worst cases, water can puddle on to pof a piston after shutdown, causing a hydraulic lock and catastrophic failure upon the next start-up. No oil can combat a significant internal coolant leak.

Water, as a by-product of combustion, can also find its way into the crankcase past the piston rings. This is normal and high equality engine oils, such as Caterpillar DEO, have additives to hold small amounts of water in suspension. But just as with soot, oxidation, nitration and sulfation, the ability of the oil to fight the effects of water is limited. Water condensation in the crankcase is accelerated by cool jacket water temperatures caused by malfunctioning thermostats, short operating times, frequent starting, cold/moist climatic conditions, extended idling during cold weather and/or operating conditions resulting in low operating temperatures.

6. Glycol – Ethylene glycol, which can enter the engine from the cooling system, forms a thick, tar-like substance that greatly reduces the oil’s lubricating properties and acts as an oxidation catalyst. Minute amounts of glycol may not show up on tests because small amounts can be destroyed by the operating heat of the engine.

The classic signature of a significant coolant leak in engines using Cat Diesel Engine Antifreeze Coolant (DEAC) is a positive reading for water and glycol, plus an increas ein copper, silicon and sodium. The copper leaches from the cooler core tubes into the oil as a result of chemcial reaction between the copper tubes and ethylene glycol. Silicon and sodium are carried in with the coolant. For engines using Cat Extended Life Coolant (ELC), a coolant leak is indicated by a positive test for water and glycol, accompanied by an increase in copper, potassium and, possibly, sodium. ELC contains approximately one-third of the sodium found in DEAC. The copper is from the cooler core, while potassium and sodium are in the ELC formulation.

In some cases, wear elements may increase along with symptoms of a coolant leak. Increases in lead and aluminum signal coolant entry into the sump, causing bearing damage. An increase in iron and a slight increase in chromium indicates coolant entry into a cylinder, causing ring and liner wear. In either case, the situation is serious and must be corrected immediately. After the repair, be sure to take a new baseline sample for the engine after approximately 15 minutes of operation. Even after the coolant leak has been repaired, it may take on or two oil changes before all elements return to normal trend levels. This is because carry-over contaminants/debris are left on internal engine surfaces.

7. Fuel – Fuel can enter the combustion chamber as a result of faulty fuel injectors or frequent starting, especially in cold weather. Most severe cases of fuel dilution are a result of leaking fuel transfer pump seals. This unburned fuel washes the oil film from the liners and pistons, resulting in an increase of iron and chrome. In extreme cases, the fuel dilution causes piston skirt scuffing and increase aluminum readings.

Raw fuel that works its way directly in to the crankcase will dilute the oil, reducing its viscosity and lubricating properties. In oil analysis reports this show sup as an increase in lead and aluminum (and for some engine models, copper and/or nickel) from main and rod bearings. In severe cases, fuel dilution will result in oil analysis detecting iron from crankshaft wear. The amount of fuel dilution an engine can tolerate varies among engines of various designs. The fuel dilution limit for oil in Caterpillar engines is 4%.

8. Dirt – Abrasive dirt particles usually enter the engine through the air induction system and/or through indiscriminate or sloppy maintenance practices. Dirt entry through the air induction system is usually the result of damaged air filter elements, loose or broken plumbing clamps and gaskets, or cracked plumbing lines and fittings. Changing the air filter too often can result in dirt entry. Some dirt is introduced directly into the induction system each time the filter housing is opened and the filter removed. The correct procedure is to only change the primary air filter when the air filter restriction indicator remains red after the engine is shut down. The secondary air filter should be changed every third time the primary filter is changed. Take special care when changing the secondary element to prevent dirt entry. Dirt entry thought he air induction system is usually indicated by an increase in silicon, iron, chrome and aluminum in the oil. Silicon and aluminum silicates are present in soils. Interpreters should know the ratio of aluminum to silicon in local soils within their region and use this information to verify dirt entry. Dirt can also be introduce into an engine through routine maintenance procedures. It is not uncommon for dirt to enter with new oil if dirty containers, funnels or spouts are used. Dirt that gets into the crankcase can damage bearings, and in extreme cases, crankshaft journal surfaces. Bottom end dirt entry is indicated by an increase in silicon, lead, aluminum, and in extreme cases, iron.

There will always be low levels of silicon in engine oil samples. However, the silicon trend line should be watched closely for any significant increases. If silicon increases along with other wear metal elements (chrome and iron from pistons and liners, and/or lead, aluminum and iron from bearings and crankshaft) then it is almost certain that dirt has entered the engine. If silicon appears relatively high all by itself, it could be in the formulation of the new oil since some oils have relatively high concentrations of silicon compounds in their additive package (usually anti-foaming additives). For this reason it is important to test each shipment of new oil to determine the silicon level.

9. Oil Transfer – Oil can transfer into the engine from another compartment through a defective seal. On eof the most common sources of transfer is a failed rear crankshaft seal. Oil from the transmission can transfer into the engine, causing a sudden, dramatic increase in such elements as iron, copper and aluminum. Gear driven hydraulic pumps can transfer oil into the engine if they experience a shaft seal failure.

Internal Contamination Internally generated debris can be divided into two categories: normally generated and abnormally generated. Normally Generated – All components having two or more mating parts and relative motion between them will create friction, heat and some degree of wear debris. Internal debris is generated by the break-in process, day-to-day operation and design factors such as the finish on mating surfaces, torque values, clearances and tolerances. How much debris is normally generated also depends on maintenance procedures, application, oil condition and the presence or absence of external contaminants. As aspects of these variables change, so will the normal levels of debris change. If the three variables affecting internal debris generation (maintenance/application, oil condition, external contamination) are stabilized, the levels of normally generated internal debris should also stabilize and a normal operation trend line can be established. This trend line will illustrate what wear metal levels a normally running engine will generate for a particular set of operating, maintenance and lubrication quality conditions. One of two things can change the established, normally generated debris trend line: either one or more of the three internal debris generation variables change, or the internal parts of the engine start to generate debris because of some internal problem. Normally generated wear is controlled and minimized by managing the three factors that directly impact it: maintenance/application, oil condition and external contamination. Abnormally Generated When Internal debris increase without a corresponding change in any of the three variables that affect debris generation, the debris being generated is probably a result of a mechanical and/or parts material defect. Abnormally generated wear is best described through the use of examples. An example of a mechanical defect is the loss of torque on a connecting rod bolt. This causes a chain reaction of events that

eventually ends in failure. Application/maintenance, oil condition and external contamination would have played no part in this type of failure. An example of a parts material defect failure might be a part that was not heat treated to the proper depth. After hours of normal wear, the hardened surface could be worn through to the soft metal, causing a dramatic increase in metallic debris generation. Again, this would happen regardless of lubricant quality, oil change frequency, external contamination or application (the more severe the application, the more rapid the debris generation). Another source of debris is an attachment such as a failing air compressor. In most cases the air compressor shares the same oil as the engine and will transfer debris into the engine through the circulating oil. Some water pumps also use engine oil for bearing lubrication. A significant increase in iron, tin, and chromium may indicate a failing water pump bearing. It is also possible for maintenance/support equipment to transfer debris. If a transfer pump used to pump new oil into the engine is in a failure mode it can pump failure debris (iron, lead, chrome and other elements) in with the new oil. This is not a common occurrence, but it does happen. Most of the time the problem can be spotted by the same debris pattern shwoing up in all the machines serviced by that particular pump. Abnormally generated wear can be managed by adhering to good repair and overhaul practices. However, abnormal wear caused by material defects, factory assembly and/or dealer repair practices is out of the customer’s control. Manufacturers and dealers offer warranty protection to reduce the customer’s risk in such cases. Summary ! The break point of an oil can be observed by monitoring wear metal levels. The oil has lost its

lubricating properties when one or more significant wear metals (iron, chromium, lead, aluminum) shows an increase. This could be the result of soot agglomeration, oil oxidation, sulfation or any combination of these factors.

! The oil change interval must be reduced by at least 50 hours from the oil’s break point to allow for the various factors which contribute to wear.

! It is important that all other variables (application, maintenance procedures, external contaminants, etc.) are controlled in order to limit oil degradation and wear.

! Oil change intervals should be managed by monitoring the combination of all test result trends (wear metals, infrared readings, and TBN). The infrared readings (soot, oxidation, nitration, sulfur) observed approximately 50 hour sprior to the oil’s break point should be used as the leading indicators to determine the oil change interval. Do not use the increase in wear metals as the primary oil change interval indicator. Doing so repeatedly will shorten the lift cycle of the engine. However, if a rise in wear metals is observed prior to the established infrared leading indicators, change the oil and investigate the cause of this out-of-trend occurrence.

! Oil condition degradation can cause both short-term and long-term effects. Monitor all oil sample test results, especially oxidation. Just because infared levels may not cause a corresponding increase in wear metal levels during a particular oil change interval does not mean that longer-term damage (such as sulfur attack) is not occurring.

Because of their cumulative nature, the long-term effects of oil degradation are difficult, if not impossible, to discern on a sample-by-sample basis. Therefore, the oil change interval must be reduced by at least 50 hours from the determined oil break point. This should allow some margin of safety for oxidation, a critical factor that directly impacts long-term deposit buildup. If external or internal contamination is detected during the Project correct the problem, change the oil, and take a baseline sample. Once the problem has been corrected, the engine may be continued in the Project unless the engine has suffered significant damage.

Section 6 – Controlling the Variables: A Checklist Managing an oil change optimization Project requires close monitoring of the cause-and-effect relationship between the variables that impact the amount of wear and rate of wear generation in an engine. Optimizing oil change intervals is a matter of determining how well the oil you have chosen will hold up to your specific set of conditions. All factors that could have an impact on the oil condition (other than hours of use) must be controlled, stabilized and held constant during the evaluation period. Oil hours is the only factor that can be allowed to vary. As much as possible, the following factors must be held constant during the evaluation period. # Engines The most desirable engines for inclusion in the project should be relatively new with low

hours and no prior history of repairs or extended oil changes. # Optimally Tuned Engine Keep engines optimally tuned. Check boost, timing, fuel settings,

air/fuel ratio control and transmission shift points to be sure there is not a potential malfunction or adjustment that might adversely affect operating temperatures and fuel consumption.

# Oil Cat DEO CH-4 or CG-4 are preferred. Other API CH-4 or CG-4 multigrade oils may be used,

but please note that it is common to find two or more different oil sin these classifications sold by the same oil company. There are performance differences among these oils. These differences are usually reflected in the price. If CH-4 oil is not available in your locality, use the best quality CG-4 oil you can get (preferably Cat DEO).

# Oil Filters Use the same filters for all engines in the test group and change them all at the same

intervals. Cat filters are preferred for their quality and strength. # Fuel Use distillate #2 diesel fuel that conforms to the specifications in Caterpillar Machine Fluid

Recommendations, SEBU6250-08. Also, fuels containing used engine oil or residual components should not be used.

# Cooling System Maintenance Be sure the cooling systems on all test units are optimal, radiators

are kept clean, and coolant is properly maintained. Engine overheating and/or overcooling, or a system failure will adversely affect the Project results by increasing oil oxidation and/or sulfur products formation. Evaluating the coolant with S•O•S coolant analysis Level 1 and Level 2 tests is an important adjunct to the S•O•S Oil Analysis tests.

For best results, all coolant should be changed to Cat Extended Life Coolant (ELC). If not equipped with ELC, the systems should be properly cleaned and flushed three or four times before changing to ELC. If you don’t flush adequately, scale from the previous coolant may flake off the inside surfaces of the cooling systems due to the differences in coolant formulations. This debris can plug cooling system passages and cause overheating. If ELC is not used, the conventional heavy duty coolant (DEAC) should be checked with S•O•S Level 1 coolant analysis. If necessary, bring the coolant up to specifications. All radiator cores

should have an external inspection periodically to assure they are free of debris and plugging. Perform S•O•S Level 1 coolant analysis at each oil change. A Level 2 analysis should be done at each fourth oil change during the Project and annually thereafter. If problems are found in a Level 1 analysis, Level 2 analysis should be performed immediately.

# Air Filters Change filters only when indicated by the air filter restriction indicator. Use the same brand and type for all units in the test group (preferably Cat filters). Also be sure to inspect the air inlet system for leaks and make repairs if necessary.

# Application Apply the same load in the same terrain, altitude and climatic conditions. If possible,

monitor fuel consumption to assure a constant load factor. # Operating Practices Different operating techniques can change how an oil responds and holds up

in an application. Excessive lugging, long periods of idling, fuel throttle on/off, hot shutdowns and other practices can affect oxidation, sooting and other potential problems. Note any operational shortcomings and bring them tot your customer’s attention as soon as possible.

# External Contamination Baseline sample each engine in the test group at every oil change to

make sure no external contaminants were introduced with the new oil. Sampling Instructions There are four common categories of oil samples involved in evaluating an oil change interval: ! New Oil Sample ! Baseline Samples ! Samples at Shortened Intervals ! Samples at Oil Changes New Oil Sample – A sample of the new oil is needed as a test reference. This must be the exact same oil as the used oil to which it is being compared. If a new shipment of oil is received, a sample of the new oil from the most recent shipment must be submitted as the reference, even if it is the same brand, type and classification as the previous oil. Baseline – After changing the oil and filter, tun the engine up to normal operating temperature (generally about 15 minutes) and take a sample. This reveals carryover from any oil left in the pan after the previous change. It also determines whether any external contaminants were introduced through the oil fill process. Take a baseline sample after every oil change. Shortenend Sample Interval – Initially, sample at 75, 150, and 250 hours. These samples establish an average rate for both oil condition and wear generation during the manufacturer’s recommended oil change interval. After establishing average base rates for the standard 250-hour oil change interval, an extended interval evaluation may begin. When extending beyond the published 250-hour change interval extend each drain interval in 50-hour increments (Refer to chart in Section 8). It is important to monitor the oil

condition and wear generation closely when exceeding the recommended oil change interval since the oil degradation rate will increase more rapidly at some point. Oil Change Take a sample each time the oil is changed. Sampling Valves All of the engines for the Project should be equipped with oil sampling valves. This will make it faster and more convenient to take samples and help assure they will be taken on time. More importantly, it will provide a representative sample of warm, well mixed oil for every sample. Sampling valves also greatly reduce the chance of introducing contamination during the sampling process. Samples taken using a vacuum pump are less representative of the oil in the system than those taken from oil sampling valves. Samples from drain streams are not acceptable for monitoring the Project engines. Refer to Special Instruction, SEHS9043, Installation of Oil Sampling Valves. Sample Information The basic information requested on the oil sample card or level is critical. Required information includes the total hours on the unit, the hours of use on the oil and make-up oil quantities since last oil change. Monitoring make-up oil is vital to accurate sample data interpretation. You should not attempt to establish extended drain intervals unless make-up oil is accurately reported. All sample data must be adjusted for both hours on the oil and for the quantity of make-up oil. Do not attempt to establish optimal oil change intervals without careful consideration of data trends after adjusting or “normalizing” for hours on the oil and for make-up oil. The formula for normalizing wear rate analysis data is: Ppm/hour (Sump capacity + make up oil/Sum Capacity) = ppm/hour (normalize for make up oil)

Section 7 – Steps to Determine an Optimal Oil Change Interval 1) Determine Engines to be Included If there is a fleet of identical models, three or more units

(depending on the fleet size) should be used in the Project. Closely following multiple units will allow data trend comparisons among the engines in the Project. This will help you reach a conclusion that you and your customer are comfortable with. If there is only one engine (or machine) of a particular model, the oil sample tests for each extended oil change interval should be repeated at least twice to assure data trends are repeating.

2) Take a Baseline Sample Note the amount of wear metal carryover. If the sample indicates the

presence of fuel, water or glycol, or excessive silicon, investigate the cause and make needed repairs. Change the oil and filter and baseline sample again to verify the problem has been solved.

3) Take Samples 75, 150, and 250 hours Establish both oil degradation (infrared analysis) and wear

metal generation rates for the normal 250-hour oil change interval. Do this for at least two oil change intervals. This provides the average rate for both oil condition and wear generation during the manufacturer’s suggested 250-hour oil change interval. These rates, established during the 250-hour interval, become the basis for comparison during the extended interval. A significant change in either the infrared or wear metal rates during the oil change period beyond 250 hours would indicate either the breakpoint of the oil or the possibility of a mechanical problem.

4) Evaluate Oil Condition and Wear Metal Rates

The results of each sample should be carefully compared to those of the previous samples to determine if the oil is fit for further use and whether the break pint has occurred. Oil condition should not exceed the following parameters: Wear Rate Analysis Rapid increase in wear metals as determined by trending External contamination (must be rectified before continuing the Project) Infrared Analysis by FT-IR Soot Level: Rapid increase in level or rate as determined by trending. Oxidation Level: 0.30 ABS/cm Sulfation Level: 0.30 APS/cm, or > the soot level Nitration Level: 0.20 ABS/cm Fluid Contaminants Fuel: 4% Water: 0.5% Glycol: No glycol TBN and TAN TBN Level: Not less than one-half the original TBN by ASTM 2896 titration method* TAN Level: Oil TAN not to exceed 3.0 or more than 2.0 above the original TAN of new oil

by ASTM 664 titration method*. *Alternatively, the Dexil TBN and TAN kits may be used, but it is suggested that two tests be performed on the sample for comparative purposes to assure accuracy. Viscosity Kinematic Viscosity – not more than 3 cst increase or decrease by the ASTM D445 procedure. (Note: kinematic viscosity is not a required test for the Project. However, it is desirable to monitor kinematic viscosity for any engine model for which the user wishes to extend engine oil intervals.) If the oil sample exceeds any of these parameters it is no longer fit for use in Caterpillar engines. Note that the wear metal break point most likely will occur before the absolute oil condition limitations have been reached. The break pint is determined by observing the rate of wear metal increase relative to infrared analysis results.

5) Repeat Oil Analysis to Verify Results

Do not make an oil change optimization decision based on one series of oil samples. Repeat the oil samples at 75, 150 and 250 hours to verify the initial findings. Once you are comfortable that the break point is beyond the 250 hour interval you may proceed to step 7. If the break pint is below 250 hours go to step 6.

6) Reduction Below the Published Oil Sample Interval

If the break pint has occurred between 150 and 250 hours, it will be necessary to reduce the oil change interval. During the second cycle of samples take samples at 75, 150, 175, 200, 225, and 250 hours. Observe where the war metal rates and oil condition show a significant increase. This is the break point for this oil in this application. The optimal oil change for this oil would be 25 to 50 hours prior to the break point.

7) Extension Beyond the Published Oil Sample Interval

If the evaluations in steps 4 and 5 determine that the break pint has not occurred you may proceed with establishing an extended oil change interval. It is suggested that you proceed in increments of 50 hours beyond 250 hours. You should sample at 250 and 300 hours for this initial step and change oil and filter at 300 hours. If the break pint appears not to have occurred before 300 hours, confirm this with one or two more series of samples before proceeding with 350 hours. As the oil change interval is walked out beyond the published 250 hour interval you should observe greater caution with each newly extended interval. You may wish to pause at certain intervals (say 350 or 400 hours) for a number of oil change periods to assure that you and the customer are comfortable that engine life is not being reduced by extended oil changes.

8) Record All Important Maintenance Information

Keep an up-to-date history of all inspection reports, minor adjustments, maintenance procedures and repairs performed during the evaluation period. Also keep and accounting of fuel and oil consumption (make-up oil). Fuel consumption data is a measure of load factor. Oil consumption is a general indication of the engine’s health, but a very important consideration for accurate interpretation of oil sample data. These records are valuable in determining which of the variables

may have had an effect on a change in the S•O•S results. Also, the quantity of make-up oil can have a significant bearing on oil analysis results. It is imperative that make-up oil be reported.

9) Results Documentation

To provide a conclusion, data accumulated during the Project must be tabulated, plotted and interpreted. A recommendation for an extended oil change interval, should be made only after carefully following the procedure outlined in this manual. We strongly urge that if an extended interval of 450 or 500 hours is established that sampling continue at each 250 hours of oil use as well at oil change time. Caterpillar dealers who become involved with customers in optimizing oil change intervals should retain the detailed documentation and recommendation records in the event that questions arise in the future. These records are also excellent for comparisons in subsequent Projects.

Section 8 – Sampling and Oil Change Schedules Sample and Change Number of

Oil Samples

Number of Coolant Samples

Interval Hours

Elapsed hours (SMU)

Baseline (Sample oil and coolant) 1 1 (Level 2) 15 min to 1 hour

First Sampling Cycle 75 hrs. (Sample oil) 150 hrs. (Sample oil) 250 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle*

3 1 (Level 1) 250 250

Second Sampling Cycle* Baseline (Sample oil) - Optional** 75 hrs. (Sample oil) 150 hrs. (Sample oil) 250 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle

4 1 (Level 1) 250 500

Third Sampling Cycle Baseline (Sample oil) - Optional** 250 hrs. (Sample oil) 300 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle

3 1 (Level 1) 300 800

Fourth Sampling Cycle Baseline (Sample oil) - Optional ** 300 hrs. (Sample oil) 350 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle*

3 1 (Level 2) 350 1,150

*This second sampling cycle may be omitted if the engines in the Project have good oil analysis trending results from consistent sampling prior to the Project. **Baseline samples are recommended after each oil change. However, if previous sampling has verified good maintenance practices and no problems were found during the previous samping cycle, the baseline sample may be omitted.

Section 8 – Sampling and Oil Change Schedule (Cont’d) Sample and Change Number of

Oil Samples

Number of Coolant Samples

Interval Hours

Elapsed hours (SMU)

Fifth Sampling Cycle Baseline (Sample oil) -Optional** 350 hrs. (Sample oil) 400 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle

3 1 (Level 1) 400 1,550

Sixth Sampling Cycle Baseline (Sample oil) -Optional** 400 hrs. (Sample oil) 450 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle

3 1 (Level 1) 450 2,000

Seventh Sampling Cycle Baseline (Sample oil) -Optional** 450 hrs. (Sample oil) 500 hrs. (Sample oil and coolant, change oil) Review and trend oil test results for this cycle

3 1 (Level 1) 500 2,500

Total to reach a 500 hour interval (7 Oil Changes)

23 Oil Samples

(17 if optional baseline samples

are omitted

6 Level1 Samples 2 Level 2 Samples

2,500 Total Oper. Hours

2,500

**Baseline samples are recommended after each oil change. However, if previous sampling has verified good maintenance practices and no problems were found during the previous sampling cycle, the baseline sample may be omitted.

Section 9 – Reference Glossary of Terms API – American Petroleum Institute – Established classifications and performance standards for lubricating oils. ABS/cm – Absorbance Units Per Centimeter – The unit of measurement for oxidation, nitration, sulfation and soot, as measured by the FT_IR instrument for Oil Condition Analysis. ASTM – Amercian Society for Testing Materials. Establishes test procedures to assure standardization of laboratory results. Break Point – The point at which an oil begins to lose its lubricating properties and wear metal generation increases significantly. DEAC – Diesel Engine Antifreeze/Coolant. Used by caterpillar as the coolant for factory fill until 1997. ELC – Extended Life Coolant. Adopted by Caterpillar as the coolant for factory fill during 1997. Nitration – Nitration is a by-product of combustion. It occurs when nitrogen and oxygen in the air combine at high temperatures and pressures in the combustion chamber of a natural gas engine, forming nitrous oxides (NO). As the nitrogen is oxidized I forms acids that wash into the oil and deplete the oil’s additives. Oxidation – Oil oxidation occurs when oxygen molecules in the crankcase air combine with the oil and certain additives. Oil oxidation results in a chemical change in the oil formultion and loss of lubricating properties. Project – For purpose of this guide, the process of optimizing oil change intervals is termed the “Project”. Sulfation – Sulfur oxides form when sulfur-containing diesel fuels are burned. When these sulfur oxides combine with water they form acids. Sulfuric and other acids signal danger to metal engine parts, causing corrosive wear to the surfaces of valve guides, piston rings and liners. TAN (Total Acid Number) – A measurement of the acids that are formed as an oil and its additives oxidize. The test for TAN is defined by ASTM D664. TBN (Total Base Number) – Additives in an oil formulation contain alkaline compounds that neutralize acids. TBN is the measure of reserve alkalinity in the oil. Generally, the higher the TBN, the more reserve alkalinity capacity the oil contains. The test for TBN is defined by ASTM D2896. Viscosity – The measure of a fluid’s resistance to flow (the oil’s internal friction). Absolute viscosity divided by the fluid’s density (weight/volume) provides the fluid’s kinematic viscosity. Kinematic viscosity determined at specific temperatures (40° C and 100° C) provides important information about oil’s ability to maintain an adequate boundary of lubrication between two moving parts. Kinematic viscosity is defined by ASTM D445.

Information Supplements Operation and maintenance Manual Supplements • Caterpillar Machine Fluids Recommendations, SEBU6250 • Caterpillar Commercial Diesel Engine Fluids Recommendations for Lubricants, Diesel Fuel and

Coolants, SEBU6251 • Caterpillar 3600 Series Diesel Engine Fluids Recommendations for Lubricants, Diesel Fuel and

Coolants, SEBU7003 • Caterpillar On-Highway Diesel Truck Fluids Recommendations for Lubricants, Diesel Fuel and

Coolants, SEBU7003 • Caterpillar Gaseous Fuel Spark Ignited Engines Lubrication Specifications, SEBU6400 • Maintenance Management Schedules for Industrial and EPG Spark Ignited Gas Engines, SEBU6127 Other Information • Optimizing Oil change Intervals – Diesel Engines, (Customer Bulletin) PEDP7035 • Installation of Oil Sampling Valves (Special Instructions), SEHS9043 • How to take a Good Oil Sample (Customer Publication), PEHP6001 • Obtaining a Representation Sample for S•O•S Oil Analysis (Fluid Analysis Laboratory Guide

Bulletin), SEBF3116 • Piston, Ring and Liner Failure Analysis, (Applied Failure Analysis reference book), SEBV0553. • Oil and Your Engine, SEBD0640 • Diesel Fuels and Your Engine, SEBD0717 • Coolant and Your Engine, SEBD0970 • Know Your Cooling System, SEBD0518