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LUBRICANT ADDITIVES

and

THE ENVIRONMENT

ATC Document 49 (revision 1)

December 2007

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Lubricant Additives and the Environment

ABSTRACT

The Technical Committee of Petroleum Additive Manufacturers in Europe (ATC) has carried out an analysis ofthe size and nature of the engine lubricants market in the 15 countries of the European Community (EU-15).

The first edition of this study was prepared in 1993 and was conducted to develop information which was notpreviously available, with the purpose of putting in perspective the benefits to the environment and the end-userprovided by lubricant additive technology. This edition (2007) updates the information and reanalyses the data.

This document describes the chemistry and functions of lubricant additives, as well as their role in thedevelopment of advanced engine systems. Product health and safety aspects are reviewed. The environmentalfate of crankcase lubricant additives is explored, and a mass balance from cradle to grave is presented.

INTRODUCTION

This paper has been prepared by a task force onbehalf of the ATC - The Technical Committee ofPetroleum Additive Manufacturers in Europe.

The petroleum additive industry is developingtechnologies and materials for the supply of serviceproducts for engines and motor vehicles, in co-operation with the petroleum and automotiveindustries, amongst others.

While the activities of the industry are very wellknown to its customers in the oil industry and to itsindirect customers in the motor industry, there isvery little public domain literature available. As aresult, it is sometimes difficult to answer relativelysimple questions’ from government regulators andothers who feel a need to know more about ourindustry and particularly its impact on theenvironment.

Aim

The aim of this paper is to introduce ATC, toexplain how the association operates, and todemonstrate the contribution lubricant additivesmake towards industry, the consumer and ultimatelythe environment.

By answering questions, the paper hopes to allowindustry and regulators to focus on the priorities for

future attention rather than things which are trivialor already well known.

Scope

The document confines itself to a study ofautomotive crankcase oil additives, their chemistry,the benefits they provide and their fate in theenvironment. Automotive crankcase oil additivescomprise those used in passenger car diesel andgasoline engine lubricants (PCMO - passenger carmotor oil) and in bus and truck diesel enginelubricants (HDDO - heavy duty diesel oil).

The study is based mainly on the 15 EuropeanCommunity members (as of April 2004) comprisingAustria, Belgium, Denmark, Finland, France,Germany, Greece, Ireland, Italy, Luxemburg,Netherlands, Portugal, Spain, Sweden and the UK.This choice was based on the availability of thewidest range of data to allow cross checking forconsistency.

ATC

The Technical Committee of Petroleum AdditiveManufacturers in Europe (ATC) was established in1974 for member companies to discuss topics of atechnical and statutory nature which were a concernto their industry. The current members are shown inTable 1. Further information about ATC can befound on the website www.atc-europe.org.

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Afton Chemical

Baker Petrolite

BASF

Chemtura Corporation

Chevron Oronite

CIBA Specialty Chemicals

Croda

Evonik RohMax Additives GmbH

Infineum

Innospec Fuel Specialties

Lubrizol

Rhodia

Table 1. Members of ATC

Membership is open to all additive companieswhich operate chemical processes for themanufacture of petroleum additives, or havecomprehensive test facilities in Europe.

In 1979, ATC became affiliated as an industrysector group of Cefic, a federation of associationsrepresenting European chemical manufacturers.

ATC organisation and objectives

The ATC organisation comprises a main committeeand sub-committees responsible for

Health, Safety and Legislation

Lubricant Performance Testing

Fuels

Quality Monitoring

External representation and strategy

In addition, the Technische Vereinigung fürMineralöl-Additive in Deutschland e.V. (TAD) co-ordinates activities for ATC in Germany.

The objectives of ATC are:

To provide a forum for additive companies tomeet and discuss developments of a technicaland/or statutory nature concerning the

manufacture or application of additives in fuels,lubricants and other petroleum products.

To ensure dissemination of ATC views torelated international and national technicalgroups and organisations.

To participate in work of a technical nature inconjunction with associated industry or statutoryorganisations or groups.

For example, ATC has developed descriptiveterminology for products to assist legislators byproviding standardised industry reporting whilstprotecting confidentiality. Technical data are sharedto provide accurate labelling of products whererequired. More recently ATC has activelyparticipated in discussions on aspects ofenvironmental legislation including REACH(Registration Evaluation and Authorisation ofChemicals).

By communicating with associated industries andtechnical bodies (e.g. ACEA, Association desConstructeurs Européens d’Automobiles; CEC,Coordinating European Council for theDevelopment of Performance Tests for Lubricantsand Engine Fuels; ATIEL, Association Techniquede 1’Industrie Européen des Lubrifiants;CONCAWE, The Oil Companies’ EuropeanOrganisation for Environmental and HealthProtection) technical issues can be pursued anddeveloped for mutual interest. The ATC alsoprovides a focal point for the industry tocommunicate with government bodies.

The petroleum additive industry

The petroleum additive industry is a research anddevelopment intensive industry and its products aremarketed solely to industrial users. Some key factsabout the petroleum additive industry are:

World-wide the industry spends about €400million/annum (2005) on research anddevelopment, of which €115 million is spent inEurope (EU-23).

World-wide the industry has a turnover of about€7,000 million of which the European market isabout €1,900 million.

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The industry employs directly about 2,800people in Europe and about 8,400 globally.

The industry operates more than 25 research anddevelopment establishments and manufacturingsites in Europe, and more than 75 globally.

The petroleum additive industry in Europe is amajor exporter.

ATC member company objectives include thedevelopment of additives for fuels and lubricants inco-operation with the oil and motor industrieswhich meet present, and future performance andenvironmental legislation cost-effectively and whichsolve or mitigate both existing and anticipatedproblems of vehicle or engine operation.

The automotive crankcase lubricant additivebusiness

All automotive crankcase lubricants need additives,at total concentrations (as sold) of typically 10 -30%. Lubricant additives help provide theperformance necessary for efficient operation andprolonged engine life.

No single additive component can do everything.Several additive components are needed to deliverthe performance required. Performancerequirements change as engine design, operatingconditions, legislation, and source of supply andprocessing methods of the base oil change. Severaladditive components of different chemistry areused, at concentrations (in the finished lubricant)from 0.005% to more than 10%. The particularcombination of additive components used in anautomotive engine oil is generally known as anadditive package. The customer (an oil company)specifies the performance requirements of thefinished lubricant. The petroleum additive supplierevaluates combinations of additive componentsuntil the required performance is achieved. Theadditive package is then offered for sale withoutdisclosing proprietary details of its composition.

Development of a new lubricant

New lubricants are developed to meet both changesin, and new, Original Equipment Manufacturer(OEM) needs, or consumer requirements. For

example, a new engine design configuration mayrequire improved lubricant performance. Equally, adifferent service application or lubricant draininterval may require changes in lubricantperformance. These requirements are identified andnew or existing engine tests and other evaluations ofphysical characteristics or performance propertiesmay be prescribed to ensure these requirements aremet.

The lubricant marketer identifies the necessaryproduct characteristics to meet the consumer needs.Commercial requirements, together with technicaltargets, are evaluated by the additive companieswho then carry out the engine tests necessary todevelop the lubricant. In many cases these test datawill be presented to an industry body or an OEM forlubricant approval.

On completion, the new lubricant (containing theadditive package) will be offered for sale therebysatisfying the OEM and market-place need.

Cost, complexity and confidentiality

The costs of engine testing are high becausecomprehensive documentation and statistically validdata are required. For example, the engine testdevelopment costs for a crankcase lubricant suitablefor use in today’s European and US diesel andgasoline engines are at least €1 million. Thispresumes the existence of a considerablebackground of in-house data and formulation skills.The latter are extremely important as many of therequirements are conflicting (i.e. use of an additiveto improve Test A could make Test B worse).Apart from running engine tests, extensive fieldtests in vehicles, often extending to millions ofkilometres, are needed to guarantee performance.

To meet the ever-changing needs of the enginedesigner and of the consumer, always with respectto environmental concerns, the additive industryputs a major effort into developing the products itsells. Many of these developments fail to meet theirtechnical targets, but some pass all the tests andbecome commercial products. The additiveindustry spends more than €115 million/year in EU-23 on new developments. A single component cancost between one and ten million Euros to developand the cost of development plus that of the

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manufacturing plant can take ten to fifteen years torecover. The cost of compliance with health andsafety legislation has risen over the years, and willincrease still further when REACH is implemented.

Petroleum additive companies require considerablefinancial investment and the innovative skill of theiremployees to develop additive components andpackages. They are selling performance productsand not commodities. Suppliers do not disclose thecomposition of additive packages, as the results oftheir investment in research and development wouldbe available to anyone having access to thecomposition. If compositions were disclosed, theincentive for companies to innovate woulddisappear.

A lack of innovation could have seriousconsequences. Today’s engines will not function onyesterday’s oils. Tomorrow’s engines will neednew additive developments. Improvements in fueleconomy alone will require additive developmentsto meet higher engine temperatures and lowerfriction requirements as well as compatibility withnew materials.

Patents, for various reasons offer only limitedprotection - one being the difficulty of policing dueto problems of analysis. Combinations ofcomponents in an additive package to achieve therequired performance may not be readily patentable.Therefore, many such inventions are treated asproprietary compositions without additional patentprotection.

To ensure continued investment in R & D andinnovation to meet the needs of the automotiveindustry and the consumer, the additive industryrequires confidentiality of the exact chemicaldescriptions of components and exact compositionof additive packages. To satisfy both thisrequirement and the current legislative requirement

for disclosure of hazardous ingredients on theSafety Data Sheet (SDS), the ATC has establishedan international nomenclature system describingchemical ingredients in terms of their key functionalgroups1. This nomenclature ensures that accurateand unambiguous health and safety information onall products can be provided which is recognised byindustry downstream users and emergencypersonnel worldwide2. This nomenclature system isalso used by international regulatory bodies.

HISTORY OF ADDITIVESDEVELOPMENT

The pre-additive period – until 1932

Until the 1930s crankcase engine oils contained noadditives, comprising only base oils. Oil drainintervals were necessarily very short (1,500 km orless) to ensure adequate lubrication. The existingoil classification system, first adopted in America in1911 by SAE (American Society of AutomotiveEngineers) was related only to oil viscosity and notperformance.

However, due to increasing consumer demands andeconomic pressures, internal combustion engineswere becoming more sophisticated. Engine oilswere becoming more stressed, giving rise to a needfor additives.

The main steps of lubricant additivedevelopment - 1930s to the present

Figure 1 gives a chronological view of thedevelopment of the main additivefamilies3,4,5,6,7,8,9,10,11,12,13. These developments havebeen driven by new specification demands imposedby engine design changes, which in turn are aresponse to consumer demand and emissionsrequirements.

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1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s and beyond

Pour Point Depressants

Antiwear Agents - ZDDP

Phenate Detergents

Sulphonate Detergents

Salicylate Detergents

Ashless Antioxidants

Viscosity Modifiers

Ashless Dispersants

Friction Modifiers

Ashless Antiwear

Figure 1. Development of lubricant additives

Main additive component families

Pour point depressants (1932)

Zinc dialkyldithiophosphates (ZDDP)antioxidant /antiwear agents (1940)

Detergent sulphonates and salicylates (1940s)

Detergent phenates (1950s)

Polymeric viscosity modifiers (1950s)

Ashless dispersants (1960s)

Inhibitors (1970s)

Friction modifiers (1970s)

Ashless antiwear (1990s)

Further diversification within each additive familycontinues. This development is driven by newlubricant specifications, which in turn are driven byevolution in engine design to meet more stringentemissions legislation and increasing consumerdemands.

Main crankcase oil classification currently usedin Europe

ACEA (Association des ConstructeursEuropéens d’Automobiles)

API (American Petroleum Institute)

OEMs (Original Equipment Manufacturers)

Functions of engine oils and additives

Friction reduction between moving surfaces -preventing metal to metal contact which leads torapid wear, and at the same time preventing lossof useful energy through heat due to excessivefriction.

Corrosion protection of the engine parts - byinhibiting chemical attack from a wide varietyof contaminants (water, acidic combustionproducts, particulate matter, etc.)

Heat transfer by acting as a coolant.Lubricants remove heat generated by friction,the combustion process and other sources, bytransfer from contact with substances at highertemperatures.

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Operating at extremes of temperature - thehighest occur under high engine loads and highoutside temperatures; the lowest at cold enginestart at low outside temperatures.

Engine seals protection to avoid oil leakageand ground contamination.

Suspension of crankcase oil contaminantssuch as combustion by-products and wear debrisuntil removed by the oil filter. Small particlesare dispersed in the lubricant, and engine partsare kept clean.

Ensure continued efficient performance ofexhaust gas after treatment systems.

Base oils or synthetic base stocks alone cannotprovide all the engine lubricant functions requiredby a modem gasoline or diesel engine. Over the lasteighty years a number of chemical additives havebeen developed (Figure 1) to enhance base stockproperties, overcome their deficiencies and providethe new performance levels required by thetechnological evolution of engines or by newregulations. As base oils continue to evolve withincreased use of hydrofinishing and hydrocrackingat the refining stage, along with new productionmethods such as Gas to Liquid (GTL), the additivesrequired will continue to evolve in parallel.

These developments have led to a wide range ofbase stock classifications, Groups I to VI, based onthe saturates level, sulphur content and viscosityindex (VI) properties of the oil (Figure 2).

CHEMISTRY OF LUBRICANTADDITIVES

Lubricant additives fall into two categories:

those protecting metal surfaces in the engine,such as antiwear, anti-rust, anticorrosion andfriction modifier additives; and,

those reinforcing base stock performance, suchas antioxidants, dispersants, viscosity modifiersand pour point depressants.

Detergent additives play a part in both areas.

Figure 2. Base stock classification

Oil soluble materials

Most lubricant additives are oil soluble materials.In fact, many are prepared using oil as a solvent.For storage stability and handling reasons, manyadditives are made as 45 - 90 wt. % concentrates ofactive material in oil. Polymeric additives used asviscosity modifiers can be diluted even more tofacilitate handling.

Additive molecules typically have long, oil soluble,hydrocarbon (non-polar) tails and smaller,hydrophilic (polar) head groups (Figure 3). Sincethe two parts of the molecule have differentsolubilities in oil, additives therefore tend to existcolloidally as inverse micelles.

Figure 3. Schematic representation of a polaradditive molecule

Detergents

Oil-soluble detergents are formed by combining apolar substrate with a metal oxide or hydroxide.

The polar substrate is made up of two parts. Thehydrocarbon tail or oleophilic group acts as thesolubiliser enabling the detergent to be fully

Polar headNon-polar oil soluble tail

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compatible and soluble in the base stock. The polarhead contains the acidic group which reacts with thebasic metal oxides or hydroxides.

Detergent polar substrates types fall into three mainclasses.

Sulphonates (Figure 4)

S

O

O

OHR

Figure 4. General structure of a sulphonate baseddetergent

Phenates (Figure 5)

OH

R

sn

OH

Ry

Where n = 1-3y = 1-3

Figure 5. General structure of a phenate baseddetergent

Salicylates (Figure 6)

OH

CO2H

R

Figure 6. Typical structure of a salicylate baseddetergent

Although several metals have been incorporatedinto detergents, only two metal cations are nowcommonly used – calcium and magnesium. Heavymetals such as barium are no longer used.

The detergent can be neutral, where the salts aresimple and contain roughly stoichiometric amountsof the metal and polar substrate (Figure 7). It ispossible, however, to incorporate large amounts ofmetal base (for example calcium carbonate) byblowing carbon dioxide through a reaction mixture

containing excess metal oxide or metal hydroxide,producing an overbased detergent (Figure 8).

Figure 7. Neutral detergent

CaCO3 core

Polar partsof surfactantmolecules

Non-polar partsof surfactantmolecule

Oil

Core size

1.25 nm - 2.25nm5% Ca - 16.5% Ca

-

-

-

-

-

-

-

--

-- -

-

-

-

-

-

-

-

-

-

--

-

-

-

-

-

-

-

-

-

Figure 8. Overbased detergent

The overbasing level is indicated by the BaseNumber (BN), measured using potentiometrictitration (e.g. ASTM D-2896) which expresses thebasicity of the detergent in terms of the equivalentnumber of milligrams of potassium hydroxide pergram of detergent.

Mode of action

Detergents reduce or remove deposits and provideanticorrosion and antirust protection. Depositprecursors, being oil insoluble, have a greateraffinity for detergent molecules than oil molecules.They are attracted to detergent micelles and trappedwithin them. Thus, they are kept in solution in theoil and cannot settle out to form deposits in theengine. On particles of less than 20nm diameter,the detergents form adsorbed films surrounding theparticle surface, which slow down coagulation.Larger particles (50 – 150nm) usually have an

n Mn+

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electrically charged surface which can attract thedetergent substrate which forms a stabilising layerthus preventing particle agglomeration.

Overbased detergents can also provide the largeamount of base required to neutralise acidiccomponents produced by fuel combustion (mineralacids) and by oxidation of the oil (organic acids).This reduces corrosive wear of the surfaces of iron(antirust protection) and other metals (anticorrosion)in the engine. Some detergent species can alsofunction as antioxidants.

Dispersants

Dispersants consist of a polar head, the polarity ofwhich is derived from oxygen or nitrogen moieties,and a hydrocarbon or oleophilic tail, typically polyisobutene, which enables the substrate to be fully oilsoluble. They are generally referred to as ashless,containing no metal to form ash on combustion, butcan also contain small amounts of boron derivedfrom boric acid which is sometimes used as acapping agent.

Three main types of ashless dispersant are in use.

Succinimides (Figure 9)

xN

HN

O

O

N

O

OR R

Figure 9. General structure of a succinimidebased dispersant

Succinic esters of polyols (Figure 10)

OH

O

O

O

RR'

OH

Figure 10. General structure of a succinic ester ofpolyols

Mannich bases (Figure 11)

OH

R

OH

R

NH

R'NH

Figure 11. General structure of a Mannich base

Mode of action

Ashless dispersants have longer hydrocarbon tailsthan the detergents but function similarly in thatthey form micelles which trap deposit precursorssuch as soot or sludge. Particles up to about 50nm(cf. 20nm for detergents) can be stabilised by thethicker adsorbed film. Dispersants which containan ionisable polar head (for example succinimides)can also stabilise larger particles by chargerepulsion. An ashless dispersant micelle can attractand hold at least ten times more sludge particlesthan a detergent micelle. Their effectiveness isshown in Figure 12. Ashless dispersants are alsohighly effective at stabilising soot produced bydiesel engines, preventing particle agglomerationand hence oil thickening.

Dispersant viscosity modifiers are ashless too, buthave a higher molecular weight. They form eventhicker barrier films by attaching themselves toparticles at several points and can stabilise particlesup to about 100nm.

Figure 12. Dispersion by dispersants

Inhibitors

Inhibitors are used to prevent, minimise or reducewear, oxidation, corrosion, rust, friction and foam.

Poor dispersancy Good dispersancy

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The main chemical families are zincdithiophosphates (ZDDPs), hindered phenols,aromatic amines, phosphorus compounds,polysiloxanes and sulphurised fatty acid derivatives.

ZDDP additives have dialkyl moieties and can besubdivided into primary alkyl and secondary alkylZDDPs. Pentan-l-ol and 3-methylbutan-2-ol areillustrative of the primary and secondary alcoholsused to prepare primary and secondary ZDDPS.

Different ZDDP chemical types perform differently(Table 2). Each type has important applications inmodern additive packages. The choice of thealcohols used in the preparation of the ZDDPdetermines the relative effectiveness of the ZDDPas an anti-wear agent but also its ability to withstandthe effects of heat and water i.e. thermal andhydrolytic stability.

PrimaryAlkyl

SecondaryAlkyl

Thermal Stability Medium Low

Antiwear Protection Medium High

Hydrolytic Stability Medium High

Table 2. Performance parameters of differentZDDP types

The general structure of a ZDDP is shown in Figure13.

P

RO

RO

S

S

Zn P

OR

OR

S

S

Figure 13. Zinc dialkyl dithiophosphates

Hindered phenols (Figure 14) function asantioxidants. Typically these are alkylated in theortho position with bulky alkyl groups to formsterically hindered phenols such as 2,6-ditertiarybutyl paracresol.

Dialkylphenylamines (Figure 15) are representativeof the chemical family of aromatic amineantioxidants.

OH

R

Figure 14. Hindered phenol

NH

R R

Figure 15. Diphenylamine

Figure 16 shows representative phosphoruscompounds used as inhibitors.

P

ORO

HRO

Dialkylhydrogenphosphite

P

ORO

ORRO

Trialkylphosphate

Figure 16. Phosphorus based inhibitors

Modes of action

Antiwear

Hydrodynamic lubrication is maintained by amultimolecular film of lubricant between thesurfaces involved. If surfaces don’t touch, there isno wear. However, hydrodynamic lubrication is notalways possible. When loads are high, or thelubricant viscosity is too low, surface asperities onthe moving parts make contact (Figure 17). Thismetal to metal contact between the lubricatedsurfaces is termed boundary lubrication. Underthese conditions, reduction in friction is achievedthrough the adhesion of the antiwear additive to themetal surface and the formation of a lubricatingsolid film.

Most anti-wear agents work by forming low shearfilms on metal surfaces. ZDDPs are by far the mosteffective multifunctional types.

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Figure 17. Illustration of boundary lubrication

The mode of action of phosphorus additives issimilar to that of ZDDP. Their function is based onthe reduction of friction during boundary lubricationthrough the adhesion of the additive or its thermaldecomposition product to the metal surface layers.

Antioxidancy and anticorrosion

Oxidation of an oil leads to the oil darkening andthickening as chemical species are broken downforming insoluble sludge or soot particles. Organicacids are produced which are extremely corrosivetowards non-ferrous metals leading, for example, tobearing corrosion. Further oxidation leads to thebuild up of polymeric material. These highmolecular weight oxygenated polymers cause oilthickening as well as varnish and gum deposits onpistons and other engine components.

Inhibitors work as antioxidants by disrupting thechain propagating steps of the oxidative process bywhich these insoluble species are formed (Figure18). The oxidative process is a chain reactionwhich once started and left unchecked increases atan exponential rate producing increasing amounts offree radical and or peroxide species. The inhibitorsthemselves function as either peroxide decomposersor as free radical traps.

ZDDPs are able to act as antioxidants by disruptingthe chain propagation steps of the oxidativereaction, by acting as either peroxide decomposersor free radical traps.

ZDDPs also act as metal deactivators oranticorrosion agents by forming protective films onmetal surfaces.

Initiation: RH R

Propagation: R + O2 ROO

ROO + RH ROOH + R

ROOH RO + HO

RO + RH ROH + R

HO + RH R + H2O

Termination: R + ROO ROOR

R + R R-R

Figure 18. Oxidation chain reaction

Hindered alkyl phenols intercept deleterious freeradicals to form stable hindered radicals which arenot prone to propagation (Figure 19). These freeradical traps help maintain the viscositycharacteristics and long term performance of thelubricant, limiting damage to the viscositymodifiers, and reducing lacquer formation from thebase oil.

OH + ROO O + ROOH

Stableradical

Radicaldimerisation

OH

HO

Figure 19. Radical Trapping by HinderedPhenols

Aromatic amines have a complementary mode ofaction to that of the phenolic family14.

Antifoam Agents

The presence of additives can slow up the release ofgases churned into lubricating oil. This may resultin foaming and/or air entrainment. Air entrainment,especially in modern, high speed, high temperatureengines, may result in diminished engine reliability.

Oil Film

LOAD

Surfaces pressedtogether under load

Oil

Increasing load

Protective layeron surface

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Foam is countered by adding tiny amounts ofantifoam additives. Silicon chemicals, such aspolydimethylsiloxanes (Figure 20) are verycommonly used as antifoam agents.

Polymethyl siloxane antifoam

SiO

Si

x

O

Figure 20. Polymethylsiloxane antifoam

Since these materials are not very oil soluble, theyseparate from the oil onto the surface of air bubblesand cause them to rupture by reducing the surfacetension. Common treating dosages for suchantifoams are between 10 to 100 ppm in oil.

Polyacrylates are particularly effective air releaseagents.

Friction Modifiers

Power loss from friction in internal combustionengines is derived from the viscous drag of thelubricant and friction losses through heat generationunder mixed and boundary lubrication conditions.The former can be reduced by decreasing theviscosity of the oil, but only to the point where alubricant film is maintained, which keeps movingparts separated.

Boundary lubrication occurs in various stressedparts of the engine, for example between rings andliners at the top of the piston travel and in the valvetrain between cam and lifters etc. In this type oflubrication the oil film is not adequate to keepmoving parts separated and this function is takenover by a film of polar molecules strongly absorbedon the metal surface. The drag caused by thisboundary lubrication depends on how easily thesesurfaces slide past one another. One way to reducethe energy losses and maintain a boundary film is byusing friction modifiers.

By definition, the base fluid itself is the primaryfriction modifier, but the need for fuel economy hasrequired additional friction modifiers. Frictionmodifiers are closely related to antiwear additives inmode of action. They are generally straight

hydrocarbon chains with a polar head group.Typical polar head groups are:

Amines, amides and their derivatives Carboxylic acids or derivatives Phosphoric or phosphonic acids and their

derivatives.

The polar head groups are attracted to the metalsurface and form relatively strong bonds whilst thelong hydrocarbon tail is left solubilised in the oil.The nature of the polar head group and the structureof the hydrocarbon chain both have a strong impacton the contribution to friction reduction.

Molybdenum compounds such as molybdenumdithiocarbamates, molybdenum dithiophosphatesand other more complex molybdenum compoundsare extensively used for friction modification.These compounds react on the metal surface to yieldmolybdenum disulphide which has a structure thatallows sliding and shearing to take place.

Examples of common friction modifier types arelisted below. Their treating dosages range from 0.1to 1.5% and chemical types include:-

Sulphurised fats and esters Amides of fatty acids Polyol esters of fatty acids e.g. glyceryl

monooleate (GMO, Figure 21) Molybdenum compounds e.g. molybdenum

dithiocarbamate (MoDTC, Figure 21)

On m

O

GMO

OH

OH

Mo

S

Mo

S

O O

SS

N

RR

SS

N

RR

MoDTC

Figure 21. Friction Modifiers

Pour point depressants

These additives act to lower the pour point of an oilwhich is the lowest temperature at which an oil willpour or flow when cooled. A low pour point isparticularly important for proper performance oflubricants in cold climates.

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The most common chemical types are thepolyacrylates and the polymethacrylates (Figure 22).

Polyacrylate

H CO2R

x

HRO2C

Polymethacrylate

CO2R

x

RO2C

Figure 22. Pour Point Depressants

At low temperatures, the wax left in the lubricantbase stock comes out of solution as wax crystals,producing a gel-like structure which impedes theflow of lubricant to critical engine parts. Pour pointdepressants are added, not to reduce the amount ofwax, but to inhibit the formation of interlockingcrystal networks.

Common treat rates range from 0.1 to 0.5 % mass inthe finished lubricants.

Viscosity modifiers

By suitable formulation, it is possible to make anengine lubricant which satisfies both the low andhigh temperature requirements of the SAE ViscosityClassification System, J300. This entails meeting,simultaneously, the limits for low-temperature W-grades (determined with a Cold Cranking Simulator(CCS) and Mini Rotary Viscometer (MRV)) andhigh-temperature grades (kinematic viscosity at100°C). High molecular weight polymers, knownas viscosity modifiers or viscosity index improversare commonly used for this purpose. Such oils arereferred to as multigrade oils (e.g. SAE l0W40).Their viscosity is less sensitive to temperature thanthat of monograde oils having the same hightemperature viscosity (e.g. SAE 40). As aconsequence, multigrade oils allow acceptableengine operation over a much wider temperaturerange. Multigrade oils have a lower viscosity at lowtemperatures allowing easier cranking and startingthan the corresponding monograde oil and as aresult improved fuel consumption. These effectsare shown schematically in Figure 23.

1

10

100

1,000

10,000

-30 -10 10 30 50 70 90

Temperature (ºC)

Viscosity (centipoise)

Monograde oilSAE 40

Typical monograde oil for hot climatesViscositytoo high at low temperatures

Monograde oilSAE 10W

Typical monograde oil for cold climatesViscosity too low at high temperatures

Multigrade oilSAE 10W40

Multigrade oil with desirable viscosity atlow and high temperature

SAE 10W

SAE 40

Figure 23. Effects of temperature on viscosity

Higher molecular weight polymers (from 50,000 to500,000) of various chemical types are used asviscosity modifiers for multigrade lubricants. Themain chemical families are olefin copolymers,hydrogenated styrene-diene copolymers (Figure 24)and polyalkylmethacrylates.

n

Ethylene-propylene copolymer (OCP)

m

n

Hydrogenated styrene isoprene copolymer

m

Figure 24. Viscosity Modifiers

For ease of application, viscosity modifiers aregenerally diluted in a low viscosity base oil to aconcentration of between 5 and 50 % massdepending on the solubility and the viscosity of thepolymer. The function of the viscosity modifiers isto decrease the slope of the viscosity /temperaturerelationship (cf. Figure 23). In addition to theirability to modify oil viscosity, viscosity modifierscan provide other functions such as dispersancy.

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This goal is generally achieved by copolymerisationof specific polar monomers (such as thosedelivering amine basicity) with the primarymonomers of the alkyl methacrylate or hydrocarbontypes.

Dispersant viscosity modifiers are often used tosupplement ashless dispersants and sometimesallow reduction in ashless dispersant level.Dispersant viscosity modifiers can exhibit goodgasoline sludge control and excellent diesel soothandling. In recent years heavy duty diesel soothandling has become one of the key issues forlubricant and engine performance as the drive toincrease oil drain intervals has grown. Somedispersant viscosity modifiers exhibit excellent soothandling and improved wear control, the latter beingdue to a reduction in abrasive wear.

Components and performance packages

Finished crankcase lubricants contain a number ofindividual additive components – typically abouteight but ranging from five to fifteen. Some or allmay be blended individually into the lubricantbasestock during manufacture. More typically, thecomponents are pre-blended by the additivemanufacturer into a performance additive packagewhich is sold to the lubricant marketer. Theviscosity modifier, which is a major component ofmultigrade crankcase lubricants, is usuallypurchased and blended separately by the lubricantmarketer. Figure 25 illustrates this schematically.

Figure 25. Component and package formulation

A performance package is therefore a concentrate ofseveral components (5 to 10 or even more) blendedcarefully together. Adjusting a performancepackage is not easy. The different components canhave synergistic or antagonistic effects on a givenperformance parameter due to chemical interactionsor competition at the metal surface. They can alsoexhibit physical or chemical incompatibility unlessformulated correctly. The development of aperformance package is technically challenging andexpensive, requiring considerable expertise.

BENEFITS OF LUBRICANTADDITIVES TO ENVIRONMENT ANDCONSUMER

The evolution of modern transportationtechnologies would be impossible without thedevelopment of advanced lubricant additives. Apartnership approach between the originalequipment manufacturers (OEMs), oil companiesand lubricant additive manufacturers has permittedadvances in vehicle energy efficiency, emissionsreduction and vehicle systems durability.

Lubricant additives are essential ingredients inmodern lubricants - performance products that helpmaintain engines, transmissions and aftertreatmentequipment in design condition for as long aspossible. This enhancement of system durabilitypermits more effective use of energy resources,maintains low levels of exhaust emissions, andprovides capabilities to employ alternative fuels,including those derived from renewable resources.A commitment to continuous advancement oflubricant additive technology facilitates theattainment of advanced engine designs to improveefficiency and conserve resources.

Petroleum conservation

Traditional lubricant base stocks are derived fromdistillation and solvent extraction of crude oil,sourced world-wide. Alternatively the crude oil maybe more highly refined including cracking andhydrotreating to produce higher quality basestocks.Some high performance formulations incorporatechemically manufactured hydrocarbons such aspolyalphaolefins (PAO) and esters. The basestocksare classified as shown in Figure 2.

Component 1

Component 3

Component 2

Component 4

Component n

AdditivePackage

Viscosity Modifier

Basestock 1

Basestock 2

FinishedLubricant

Additive Manufacturers

Base Oil Suppliers

Lubricant Marketers

15

Base stock properties can differ markedlydepending on the source of crude and the refiningprocess. Lubricant additive technology can providethe necessary enhancement to these base fluids toachieve OEM and industry standards ofperformance. This increase in performance andvalue of formulated lubricants permits moreeffective use of petroleum resources.

Fuel, which is produced from a variety of crude oilsand different refinery processes, can have variableproperties and performance. Lubricant additives aredesigned to cope with various types of gasoline anddiesel, as well as alternative fuels, to provide enginesystem durability and cleanliness. Within the pastdecade a significant shift has occurred withinEurope in that there has been a dramatic increase inthe use of diesel engines in passenger cars, drivenby fuel economy concerns and the desire to reduceCO2 emissions, as shown in Table 3. Theconsumption of diesel fuel in Europe now exceedsthat of gasoline15.

Table 3. Fuel trends in Europe

Alternative Fuels

As part of a world-wide trend, fuel sulphur levels inboth gasoline and diesel have been dramaticallyreduced. This has been driven by concerns aboutthe contribution to SOx emissions and also toenable the use of some exhaust gas aftertreatmentsystems. Lubricant additive technology, togetherwith lubricant performance evaluation tests, hasbeen modified to reflect the move toward lowsulphur fuel and increased penetration of diesel.

A variety of alternative fuels are being activelyinvestigated to develop cleaner energy sources fortransportation, to use renewable resources, and toreduce emissions. Significant further shifts areanticipated in the fuel market-place in Europe, withmovement towards fuels containing oxygenates,bioethanol and biodiesel. Longer term the use ofgas-to-liquid (GTL), biomass-to-liquid (BTL) and

other alternative fuels is expected to increase. Theenvironmental impact of these alternatives is underactive investigation.

Lubricant additive technologies are being developedto permit use of these alternative fuels17. Theseshifts continue to place demands for furtheradvances in lubricant additive design for theeffective performance of vehicles operating on thesefuels.

Fuel economy

A significant focus for vehicle systems design andlubrication is to enhance fuel economy, the objectbeing to conserve resources and reduce vehiclecontributions to emissions. Road transportcontributes 14% of greenhouse gas emissions18.The initial approach in the USA has been onCorporate Average Fuel Economy (CAFE)requirements for passenger car vehicle production.In Europe, no fuel economy improvements have yetbeen mandated. However, ACEA has reached avoluntary agreement with the EuropeanCommission to reduce CO2 emissions to a target of140g CO2/km by 2008, and a further reduction to120g CO2/km is envisaged for 2012 (Figure 26). Inaddition demands from the consumer to control fuelconsumption, reduce operating costs and to increasevehicle performance have resulted in fuel economyenhancements from the lubricant. European and USlubricant testing puts significant emphasis on fueleconomy performance. Some OEMs haveintroduced fuel economy requirements in their in-house specification, based on the CEC M111 fueleconomy test19 and other tests. These requirementsare given in Table 4.

Figure 26. Fuel economy requirements(Source: Ricardo)

% of new passenger cars using diesel fuelSource: AID Newsletter

16

1991 2000 2006 (1st

half)

15% 32% 50%

16

FE requirement in CEC L-54 (M111E) test,industry and OEM

Specification FE requirement

ACEA A1/B1, A5/B5, C1 2.5%

ACEA C3 1.0%

BMW* 1.0%

Daimler 1.0 or 1.7%

Ford 2.5 or 3.0%

Opel* 1.5%

Renault 1.0%

VAG* 2.0%

* OEM test method

Table 4. FE requirements, industry and OEM

Lubricant additives play a role in fuel economy.Friction modifiers reduce energy loss due to enginefriction. The viscosity modifier reduces viscousdrag in engine operation, enhancing efficiency.Antioxidants control lubricant viscosity, andtogether with detergents and dispersants whichmaintain system cleanliness, help retain vehicle fueleconomy characteristics.

Lubricant consumption control

In addition to significant contributions to fueleconomy, conservation of petroleum resources, withattendant reduced contribution to emissions, isachieved by enhancing lubricant economy in service(Table 5). Modern, low emission engine designscreate significant lubrication challenges for additivechemistry to control deposits and wear, andmaintain long-term low emissions performance.The combination of reduced oil consumption andextended drain intervals greatly increases the loadon the lubricant20 (Figure 27).

Lubricant additives assist in reducing oilconsumption by modifying the physical propertiesof the lubricant such as viscosity, and enable the useof less volatile base fluids. Maintaining systemsintegrity is a key function of the lubricant. Lossesdue to leakage have been almost eliminated with thehelp of oil-seal compatible lubricants.

Vehicle Engineering and Lubricant AdditiveDevelopment

Higher performance, with reduced lubricantquantity for gasoline passenger cars

(data based on top specification engines)

Model year 1949 1972 1992 2005

Power (kW) 25 74 96 120

Power density(kW/L)

21 37 45 60

Oil fill (L) 3.0 3.7 3.5 3.5

Oil consumption(L/1,000km)

0.5 0.25 0.1 0.1

Oil change interval(km)

1,500 5,000 15,000 30,000

Oil flush at oilchange

Yes No No No

Total oil used after30,000km (L)

87.0 29.8 10.0 6.5

Average fuelconsumption(L/100km)

12 10 7 7

Engine durability(1000km)

<100 175 250 250

Source: Ricardo

Table 5. Engine oil use trends

0

5

10

15

20

1940 1960 1980 2000 2020

Model Year

Stress

Stress = Engine Pow er (kW)/Total oil used in 30,000km

Figure 27. Stress on passenger car lubricant

Additive components also help control wear anddeposits, maintaining low oil consumptionthroughout a vehicle’s life.

17

Lubrication engineering

Lubricant additives are now considered aslubrication engineering design components.

Appropriate lubricant development enables newengine system designs to perform successfully.

Figure 28. Lubricant additives as design components

Parameters controlled by lubricant additive function(Figure 28) are optimised in the developmentprocess to meet the performance requirements of theengine. Results of these designs (Table 5) haveconsistently enhanced system performance withhigher power output. Lubricant additivedevelopment has permitted extended oil drainservice intervals, enhanced fuel efficiency andimproved engine durability. These factors havecontributed measurably to conserving petroleumand other natural resources.

The contribution that lubricant additives have madein the above areas may most effectively beillustrated by considering the concept of Stress onthe Lubricant. This is expressed as engine Powerper quantity of oil used per unit of distancetravelled. The quantity of oil used must take intoaccount both oil changes and top-up. Figure 27shows this graphically using the data from Table 5.The capability to absorb a sixty fold increase instress over a period of just over fifty years is almostsolely attributable to additive technology.

Exhaust emissions

Vehicle and engine system designs have to meetincreasingly stringent exhaust emission standards,Figure 29. Higher performance lubricant additives

are required to cope with the more severe engineoperating conditions in the low emissions designsbeing developed by OEMs. Vehicle maintenance isa key aspect of long term emissions control. USEPA and UK RAC tests both report thatapproximately 15% of the passenger car populationin the USA and UK causes approximately 55% ofpassenger car related air pollution21. Originalequipment manufacturers are focusing on higherperformance lubricants, more robust vehicle systemdesigns, and on-board diagnostic systems (OBD) toachieve their targets of long term integrity ofemissions systems.

Figure 29. Global emissions standards for HeavyDuty vehicles (Source: Purem)

Wear resistanceControl sludgeControl deposits (detergency)Disperse contaminantsHigh temperature performanceHeat transferReduce frictionMaintain oil film thicknessOxidation resistanceCompatibility withAfter treatment devices

Low temperature flowViscosity – shear stabilityPumpabilityCatalyst compatibleLow volatilityFoam inhibitionControl oil thickeningViscosity/temperaturerelationshipSeal compatibleControl corrosion

18

Health, Safety and the Environment

Lubricant additive packages are multi-componentblends sold to industrial customers. The risk ofexposure of these products to man and theenvironment is already tightly controlled by existingEU legislation concerning protection of workers,emissions to air, water and soil, and disposal ofwaste.

In addition to legislative drivers, the lubricantadditives industry, represented in Europe by theATC, has an ongoing commitment to provideaccurate and up-to-date health, safety andenvironmental advice to all downstream users. Inparticular, the ATC has taken an active andinformed role in communications on Health, Safetyand Environmental matters, such as providingnomenclature on additives, disclosure of appropriatedetail on composition and hazard information andproducing best practice guidelines for specificsubstances22.

Historically, additive manufacturers havecollaborated in the testing of major additive classes.A recent example of this was the voluntaryparticipation in national and international chemicalinitiatives (e.g. US EPA High Product Volume;ICCA SIDS) to generate data on a significantnumber of chemical classes, covering the mainadditive families included in crankcase lubricants.

The majority of lubricant additives are of lowmammalian toxicity2 and are typically less harmfulwhen ingested than familiar household products.Some lubricant additives are suspected of beingharmful to aquatic organisms and most show adegree of persistence but these additives aretypically of low water solubility and when handledand disposed of according to manufacturers’recommendations are considered not to present asignificant environmental risk23. Additive suppliersprovide this information to downstream usersthrough hazard communication documents such asthe Safety Data Sheet (SDS) and product label,which contain relevant instructions for safe storage,use and disposal.

The composition of the crankcase lubricant changesduring use. Some additives are chemically changedor even destroyed as part of their functionality, and

any contaminants of combustion generated duringthe course of engine operation which are not sweptinto the exhaust stream are neutralised anddispersed within the lubricant. It is widely acceptedthat used oil drained from the engine sump willcontain polyaromatic hydrocarbons generated by thecombustion process and this waste is suspected topose a carcinogen risk through accidental skincontact. A significant number of motorists routinelyperform engine oil changes themselves and soconsumer product labelling and consumer educationagainst inappropriate contact or disposal of usedlubricants is part of an active safeguards programmewithin the oil marketing industry. This, togetherwith a legal requirement to dispose of used oil atdedicated collection facilities serve to minimise theenvironmental and human risks from used oil.

The fate of the lubricant additive portion of theseproducts is discussed in more detail below.

Lubricant additives - user benefits

Lubricant additives packages are high performanceproducts. Oils made from these packages aretailored to provide proper lubrication for anyengine. Additionally, lubricants can be formulatedfor multiple applications, for example bothpassenger car gasoline and diesel engines.Formulation of multigrade lubricants containingpolymeric viscosity modifier additives for operationin climate extremes has eliminated the need forseasonal oil changes. These lubricants provide thenecessary performance to meet the vehiclemanufacturer’s warranty requirements, includingprotection of any emission control systems. Suchlubricants provide confidence to the consumer andprotect the owner’s investment in the vehicle.

Lubricant additive technology delivers significantbenefits to the consumer in controlling costsassociated with vehicle design and operation. Thecost of lubricant represents a small fraction of thetotal operating cost of the vehicle. Lubricantadditives reduce consumer costs by reducing fueland oil consumption, lowering maintenancerequirements, extending service intervals, reducingdowntime losses and enhancing vehicle reliability.Lubricant additives provide substantial benefits tothe environment and to the end user.

19

EUROPEAN CRANKCASELUBRICANT ADDITIVE INDUSTRYPROFILE

This section discusses the size and nature of thecrankcase lubricant additives business in Europe,examines the end use of additives and provides thebasis to consider their fate and environmentalimpact.

The scope of this review is limited to products usedin four-stroke internal combustion engines in roadvehicles, which represents most of the crankcaseadditive use in Europe. Other markets includingagricultural, railway, off-highway construction, twostroke engines and stationary engines are less welldefined and are excluded.

Sources of data

No public data sources give a comprehensive guideto the size of the crankcase additives market inEurope. Market information is available fromconsultants for a fee24,25. Estimates of the marketsize are also held by individual ATC membercompanies, but these are confidential.

The methodology used here has been to requestthose ATC members marketing complete crankcaseadditive packages to supply European sales data.These were sent to Cefic for analysis according totheir protocols.

The information requested by ATC to be submittedto Cefic was a detailed breakdown into componentsof the top 80% (by volume) of additive packagessold in the EU-15 countries, for both passenger carand commercial vehicle market segments. Fromthese data the total additive volume has beenobtained, which together with the additive treat rategives the total crankcase lubricant volume in theEU-15 countries. This total figure is divided intopassenger car use - PCMO - (1,270 kilotonnes/year)and commercial vehicle (truck, bus, etc.) use -HDDO - (1,330 kilotonnes/year) and is shown inTable 6. These data are also compared with theEuropaLub study26 of the EU-15 crankcase lubricantmarket.

In the previous version of this brochure, thecrankcase lubricant market estimates were based on

OECD Europe in 1990. Since then the OECD hasexpanded membership and no longer forms the bestbasis for comparisons. However, to make a linkback, the EU-15 data have been expanded to includethe 1990 OECD members. This is also shown inTable 6.

Estimatedcrankcaselubricant market(kilotonnes)based on:

PassengerCar Motor

Oils

Commercialvehicle

engine oils

Total

ATC member data(2005 – EU-15)

1270 1330 2600

EuropaLub report(2004 – EU-15)

913 744 1657

EuropaLub report(2004 – OECD-93)

973 902 1875

ATC Document 49(1993 – OECD-93)

1200 1400 2600

Table 6. Estimated crankcase lubricant market

As can be seen there is a discrepancy between theroutes. Estimating the EU-15 crankcase lubricantmarket based on additive sales leads to a higherestimate, 2,600 kilotonnes, than the lubricantmarket based on the EuropaLub report, 1,657kilotonnes. The EuropaLub report is based onlubricant sales in these countries. This ignoresadditives produced in the EU-15 and exported forblending elsewhere, and also finished lubricantexports. Both of these routes are included in theestimate based on additive sales, which as expectedis a higher figure.

Despite constant additive volumes sold in Europe,the EuropaLub data do clearly reflect that finishedlubricant volumes in Europe are declining, a trendthat has been visible for a number of years.Comparing the OECD market data from 1990 givenin the earlier publication of Document 4927 with the2004 EuropaLub data shows an annual decline of2.3% of the European lubricant market. Since thelubricant market is generally aligned with growth ofthe GDP the actual decline is even larger. Thisdecline is largely attributed to decreases in oilconsumption rates and increased oil drain intervals.

20

It is also interesting to note that the passenger carmarket has decreased less rapidly than thecommercial vehicle market. This is attributed to thelesser emphasis on drain intervals in passenger carsthan in commercial vehicles where operating costsare a greater concern.

Weighted average typical finished lubricants havebeen established for the two categories. Thelubricants are split first into their main componentcategories - base stock, viscosity modifier, andperformance package, Figure 30. The viscositymodifier and performance packages are then furthersplit into their major constituent additivecomponents, Figure 31. Simple calculations usingthe crankcase oil tonnages in Table 6 and theformulations in Figure 30 and Figure 31 give ustonnages for the principal additive components(Table 7).

Viscositymodifier

Performancepackage

Basestock

Viscosity modifier consists of varying proportions ofpolyhydrocarbon and polymethacrylate types

Heavy Duty DieselOil

8.7%

79.0%

12.3%

Passenger Car MotorOil

6.7%11.0%

82.2%

Figure 30. Finished crankcase lubricantformulations

Metal detergent

ZDDP

Inhibitor

Passenger Car Motor Oil

53.8%

26.8%11.0%

8.4%

Heavy Duty Diesel Oil

52.1%

6.3%

11.4%30.2%

Ashless dispersant

Figure 31. Additive package formulations

Market for crankcase additive componentsCalculated from weighted average typical lubricant

composition OECD Europe (kilotonnes)

Additive component PCMO HDDO Total

Performance Package

Ashless dispersant 64.7 72.4 137.1

Metal detergent 32.1 42.0 74.1

ZDDP 13.2 15.8 29.0

Inhibitor 10.1 8.8 18.9

Sub-TotalPerformance Package

120.2 139.0 259.1

Viscosity Modifiers

VM 70.8 95.5 166.3

D-VM 2.6 1.9 4.5

Sub-Total ViscosityModifiers

73.4 97.4 170.8

Total 193.6 236.4 430.0

Table 7. Market for crankcase additivecomponents

Typical performance additive packages

The concept of the typical package is a majorassumption. Hundreds of different additivepackages are on the market - all confidential to thesupplier. However, it is considered that for presentpurposes, bearing in mind the accuracy of otherdata, the typical package concept is both useful andappropriate. The following additive categories wereused: ashless dispersants, metal-containingdetergents and zinc dialkyldithiophosphates. Smallvolume specialised components, such as anti-oxidants, friction modifiers, supplemental AW - areincluded with the inhibitors. The current data arecomparable to the 1993 data by adding the calciumand magnesium detergent values in the latter.

Comparing the data in Figure 31 to the 1993 datashows some interesting trends such as the decreasein metal detergents – most visibly in commercialvehicle lubricants – due to lower fuel sulphur levelsrequire less base reserve. Also a decline in ZDDPlevels are seen which reflects the concerns on theimpact of phosphorus on exhaust gas after-treatmentsystems.

21

Viscosity Modifiers

Although there are different types of viscositymodifiers they have been combined for this purpose.Occasionally they are mixed with the additivepackage, but are more usually sold separately, withthe lubricant producer choosing one or the other.

If we look at the overall lubricant composition itbecomes apparent that the average treat rate hasincreased for both passenger car and the commercialvehicle segment. This is a reflection of theincreased performance requirements and extendeddrain intervals: enabling longer drain requires morehigh performance additives.

Most crankcase lubricants are multigrade,containing viscosity modifiers. However, somemonograde oils are still sold in Europe, but as thevolume is small no allowance has been made formonograde oils when estimating weighted averagetypical viscosity modifier concentrations.

THE ULTIMATE FATE OFCRANKCASE LUBRICANTADDITIVES

Crankcase lubricants, as identified in the previoussection are here followed through to their ultimatefate in the air, water or soil compartments. ATCmember companies seek to ensure proper use oftheir products, to develop further knowledge of therelated environmental processes, and to ensure thatappropriate information is available. Other industrypartners have placed increasing emphasis on the re-use and safe disposal of used oil. OEMs have givenmuch emphasis over the last five years to therecycling of used engine oil. The re-refining of usedoils has also increased.

Figure 32 traces the fate of crankcase lubricantsfrom sale through to the environmentalcompartments. The environmental pathways forlubricants used in the passenger car and trucksectors are the same. Thus crankcase lubricantadditives also follow these same general pathways,to their ultimate fate in the air, water or soilcompartments.

Figure 32. Flow diagram of fate of lubricants

Crankcase lubricants enter the engine when eitherthe sump is filled or when the engine is topped up.They leave the engine

in drained, used oil or

as leakage through seals or gaskets during use or

via lubricant consumption down the tailpipe asgaseous emissions (combustion products orparticulates).

If the vehicle is fitted with a particulate trap, theincombustible portion of the lubricant in the exhaustwill be trapped by this filter.

Broken lines in Figure 32 show that a portion ofused oil which is collected and burnt or incineratedcontributes to emissions in the air compartment -and that, ultimately, some emissions to the aircompartment end in the soil or water compartments.

Approximately 2,600 kilotonnes of crankcaselubricants were sold in EU-15 Europe in 2005. It isestimated that 24% of lubricants sold for bothpassenger cars and trucks is consumed duringoperation28,29. The lubricant leaves the engine downthe tailpipe as emissions of either combustionproducts (gases or vapour) or particulates (whichwill be collected if a particulate trap is fitted). Aportion of the lubricant (and fuel) combustionproducts is entrained and re-dispersed in thecrankcase lubricant itself, or forms deposits in theengine.

Lubricant Sold

Cars

Trucks

Consumption

Leakages

Oil Changes

Exhaust

Combustion

Spillage &

Dumping

Incineration,Energy Use /Combustion

Reuse

Air

Water

Soil

AfterTreatmentDevices

22

Leakage past seals or gaskets is estimated to benegligible for both cars and trucks. Theenvironmental routes of this portion of the lubricantare to the water and soil compartments.

Used oil should be drained from the crankcase,collected and re-refined and re-used, or disposed ofsuitably. Approximately 75% of lubricants sold(2,000 kilotonnes) is drained as used oil at oilchanges. This includes oil from scrap vehicles. Asignificant proportion (estimated 47%30) of thatcollected is used as fuel oil or incinerated for energyvalue or disposal. Regeneration represents anestimated 24% of the total waste oil. Additives inoils properly disposed of by these routes end up assolids for landfill, used in cement or as gaseousemissions. However, approximately 28% of usedoil is still unaccounted for and may be dumped intothe soil and water compartments, or burnt entering

the air compartment. The proportions going to thevarious pathways are illustrated in Figure 33.

Exhaust emissions24%

Incineration with

energy recovery36%

Regeneration18%

Illegal disposal

21%

Disposal

1%

Figure 33. Fate of lubricants in Europe

A model has been established based on the aboveanalysis and used by the ATC to estimate theproportions of crankcase lubricants and additivesgoing into the three environmental compartments.It is shown schematically in Figure 34.

2600

553

1976

9

291

319

1011

965

305

1330

1270

20

929

1423

474

430

78

235

57

179

147

47

236

194

1

46

326

91

153

3

Scale

1 milliontonnes

CrankcaseLubricant

Additive

Sales

Truck

Car

Consumption(Exhaust)

Oil drain

Oil drain

Consumption(Exhaust)

Unaccounted

Collected

Incineration*

Disposal

Regeneration

* Incineration withenergy recovery

Trapped

Untrapped

2600

553

1976

9

291

319

1011

965

305

1330

1270

20

929

1423

474

430

78

235

57

179

147

47

236

194

1

46

326

91

153

3

Scale

1 milliontonnes

CrankcaseLubricant

Additive

Scale

1 milliontonnes

CrankcaseLubricant

Additive

Sales

Truck

Car

Consumption(Exhaust)

Oil drain

Oil drain

Consumption(Exhaust)

Unaccounted

Collected

Incineration*

Disposal

Regeneration

* Incineration withenergy recovery

Trapped

Untrapped

Figure 34. Fate of crankcase lubricants EU-15 2005 (figures in kilotonnes)

Re-refining/re-use

It is estimated that in OECD Europe some 475kilotonnes a year of used crankcase lubricant is re-

refined. These base stocks and then used, afterappropriate treatment, in the same way as virginbase stocks. Given that the conversion processyield is typically 80%31, some 380 kilotonnes of re-

23

refined basestocks are produced annually. Thisrepresents approximately 18% of the total basestocks used in crankcase lubricants. Re-refining andre-use prolongs the life of limited natural resources.

Re-refining also produces an estimated 35kilotonnes a year of residual sludge. Afterappropriate treatment to neutralise it, the sludge isused in cement manufacture or road construction, orotherwise disposed of in landfills.

Incineration/use as fuel oil

It is estimated that up to 930 kilotonnes of used oilis burnt either as fuel oil or for heat recovery inincinerators. Again these activities providesignificant environmental benefits - it has beenestimated32 that burning one tonne of used oil savesthe use of 0.85 tonne of heavy fuel. Thesequantities include some 150 kilotonnes of additives,of which no more than 7.5 kilotonnes are elementsother than carbon, hydrogen or oxygen, and notmore than 4 kilotonnes is metallic (calcium,magnesium and zinc). Incineration is regulated inthe EC and monitored throughout the memberstates. Emissions originating from the additivecontent of used oils therefore present no new orunregulated environmental hazard.

Used oil/leakage

About 550 kilotonnes a year of used oil is eitherunaccounted for or lost. At worst, this ends up inthe water compartment, either directly or indirectlythrough the soil compartment. This used oilcontains approximately 90 kilotonnes of additives.It should be noted that these figures have decreasedby nearly 50% since the previous assessment wasmade in 1993.

The additives in used oil which could potentiallyenter the water compartment comprise mainlycarbon, hydrogen and oxygen. The quantitiesinvolved do not represent a major environmentalconcern relative to total hydrocarbon leakages inOECD Europe. However, dumping into theenvironment is unnecessary and unacceptablepollution which is being addressed by stricterimplementation of existing regulations, and anincreased focus on collection of used oil.

The remaining elements and approximate quantitiescomprise calcium/magnesium (1,350 tonnes), zinc(600 tonnes), sulphur (1,600 tonnes), phosphorus(530 tonnes) and nitrogen (350 tonnes), the use andbenefits of which are discussed in earlier sections.The performance of internal combustion enginescould not be maintained effectively without them.Research has not yet identified alternative chemicalswhich offer the same benefits of reduced emissions,enhanced fuel economy and lower oil consumption,and could be considered more environmentallybenign.

Exhaust emission calculations

The contributions to vehicle exhaust emissions fromlubricant additives have been estimated. The keyassumptions related to combustion are as follows:

All oil and additive fractions are burnt at thesame rate. This represents a worst caseassumption.

All the nitrogen in the lubricant from theadditives is converted to NOx. This represents areasonable worst case assumption.

All the additive metals burnt during combustioncontribute to particulate formation. (Also aworst case assumption for estimating theadditive contribution to particulates.)

The amount of combusted lubricant whichcontributes to engine deposits is insignificantcompared to the total combustion products.

The first assumption that oil and additive fractionsare consumed at the same rate suggests additiveconcentrations in drained oil are the same as infresh. In practice, concentrations may increase ordecrease, depending on engine type and operatingcharacteristics. There are two primary modes of oilconsumption - volatility and bulk loss. In hot-running engines designed for low oil consumption,the additive concentration will tend to increasewithin the oil drain interval, due primarily to oilvolatilisation. For calculation of additivecontributions to exhaust emissions, therefore, thefirst assumption in the model represents a worstcase scenario.

24

With modern aftertreatment systems the NOx andparticulates, both lubricant and fuel derived, will besignificantly reduced.

Finished lubricant

Weighted average formulations have been derivedfrom data supplied by ATC members as describedabove. The additive contents of Passenger CarMotor Oil (PCMO) and Heavy Duty Diesel Oil(HDDO) formulations are shown in Table 8. Themain elemental contents in the oil arising from theadditives are shown in Table 9.

Additive componentPassenger

Car Motor OilHeavy DutyDiesel Oil

Ashless dispersant 5.9% 6.4%

Metal detergent 3.0% 3.7%

ZDDP 1.2% 1.4%

Inhibitor 0.9% 0.8%

Viscosity modifier 6.7% 8.7%

Total Additive Content 17.8% 21.0%

Base stock 82.2% 79.0%

Total 100.0% 100.0%

Table 8. Weighted-average crankcase lubricantcomposition, Mass percent

Contribution from additives - weighted averages(mass %)

PassengerCar Motor

Oil

Heavy DutyDiesel Oil

Calcium & magnesium 0.24% 0.30%

Nitrogen 0.07% 0.08%

Zinc 0.11% 0.12%

Phosphorus 0.10% 0.11%

Sulphur 0.26% 0.36%

Plus other contributions to carbon, oxygen andhydrogen contents

Table 9. Elemental content of crankcase oils

Fuel consumption

The amount of fuel used is based on quoted oilindustry, EC and national government statistics15

(Table 10). For passenger cars, fuel consumption inL/l00 km is based on quoted vehicle fuel economy

figures. For trucks, the fuel consumption in g/kW.his the weighted average for different vehicle typesand populations.

Fuel Consumption OECD Europe 199815

Gasoline Diesel

Annual fuelconsumption milliontonnes

127 130

Average per vehicle Cars7 L/100km

Cars7L/100km

Trucks180g/kW.h

Table 10. Fuel consumption

Fate - by element

Table 9 shows the percentage of main elementsoriginating from additives for the weighted averagePCMO and HDDO formulations. The greatestproportion is carbon. Other elements comprise nomore than 1% of the total lubricant. The fate ofthese elements will each be dealt with in turn.Because of the experimental difficulty insegregating the contributions of all the elements inthe combustion process, some further details of theaverage assumptions are given below.

Fate of carbon

When fuel is burnt in cars and trucks, most of thecarbon forms carbon dioxide (Table 1131). Smallproportions end up in particulates and partiallyburnt hydrocarbon fractions. Data shown in table11 are for engine out emissions. Aftertreatmentdevices will remove particulates and converthydrocarbons and carbon monoxide to carbondioxide (and water). Carbonaceous particulatematter will also be converted to carbon dioxideduring the regeneration phase.

Particulates CO2 CO HC

Cars 0.1 88.0 11.2 0.7

Trucks 0.3 99.0 0.6 0.1

Source: Volkswagen33

Table 11. Fate of fuel carbon during combustion

On the basis of ATC and industry statistics15,33, thefollowing assumptions are used in the model

25

calculations: 20% of the carbon from the lubricantconsumed in trucks contributes to particulates, 20%goes to CO, 20% to hydrocarbons, 5% remainssuspended in the oil and the remainder is burnt toCO2. A similar judgement for gasoline poweredcars suggests that 5% of the carbon from thelubricant consumed contributes to particulates, 5%goes to CO, 5% to hydrocarbons, 1% remains in theoil and the remainder is burnt to CO2.

Similarly, in proportion, additive carbon contributesto the engine out emissions of carbon monoxide,unburnt hydrocarbons and particulates, and carbondioxide. These will be modified as above by theaftertreatment system.

Fate of nitrogen

The model contains the assumption that allcombusted additive nitrogen forms NOx in thecombustion chamber. Due to the relatively lowlevel of nitrogen in lubricants (Table 9) there are nofirm experimental data to support this assumptionbut, as a reasonable worst case, additive nitrogencan be also considered as a contributor to engine outNOx emissions. However since the introduction ofthe Euro IV emissions legislation, exhaustemissions of NOx from all sources have beensignificantly reduced.

Other elements

It is assumed that all the additive metals burntduring combustion contribute to particulateformation. Magnesium and calcium form sulphates,whilst zinc goes to both zinc oxide and zincpyrophosphate. The emissions of lubricant derivedmetals (S, Ca, Zn, P, and Mg) are highly correlatedwith emissions predicted from the composition ofoil (and fuel sulphur); however, recovery rates varyconsiderably (ranging from 17% for Mg to 125%for S)34.

Comparison with legislative limits

Light duty

EC regulated emission levels for passenger carshave been significantly reduced over recent years,

and are now greatly reduced compared with those inplace when this document was first issued.However, the contribution from lubricant additivesto these regulated emissions levels (Table 12)remains small, at about 0.1% for hydrocarbons plusNOx and 0.2% for CO of the regulated emissionslevel taking worst case assumptions based on engineout emissions. However lubricant additives,together with engine design improvements, havepermitted successive reductions in regulatedemissions.

Estimated emissionsEU-15 2005

Kilotonnes g/km

CO2 109 0.04

HC 2.1

NOx 0.450.001

CO 4.1 0.002

Comparison with current/future EC legislation g/km

(gasoline/diesel)

Euro 4 Euro 5

HC + NOx 0.18/0.30 0.16/0.23

CO 1.0/0.5 1.0/0.5

Table 12. Light duty engine exhaust emissions

Heavy duty

Heavy duty diesel emission limits have also beenconsiderably reduced within the EC over the years,with further reductions planned in 2009. Onceagain, the additive contribution (Table 13) toregulated emission levels of CO, NOx andhydrocarbons can be considered small.

Because fuel derived particulates have been reducedto a very low level, additives now make a relativelymore significant contribution to particulateemissions. As limits have been reduced, up to 50%of the regulated particulate weight may originatefrom lubricant additives. It must be emphasisedagain that the assumptions made to calculate theadditive contribution represent the absolute worstcase.

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Estimated additive-derived emissionsEU-15 2005

Kilotonnes g/kW.h

Particulates 7.1 0.01

CO2 45 0.07

HC 8.3 0.01

CO 16.5 0.03

NOx 0.51 0.001

Comparison with current/future limit valuesg/kW.h

Euro IV Euro V

Particulates 0.02 0.02

HC 0.46 0.46

CO 1.5 1.5

NOx 3.5 2.0

Table 13. Diesel engine exhaust emissions

These contributions to particulate emissions must beseen in the context of a considerable netenvironmental gain. Use of additives has enabledregulated particulate emissions to be reduced to thecurrent low level of 0.02g/kW.h. This has beenachieved by engine technology which would nothave been possible without additives which, atworst, will-contribute just 0.01g/kW.h to particulateemissions. The total contribution due to additivesof some 7,000 tonnes over the whole of EU-15 isrelatively small. Engine and aftertreatmentmanufacturers together with the lubricant andadditive industry continue research to reduce furtherthese emissions.

These contributions must be compared with theenvironmental benefits that the use of additives hasbrought in terms of reduced emissions and lowerfuel and oil consumption.

Contribution to unregulated emissions

Carbon Dioxide

Carbon dioxide, whilst not technically a regulatedautomotive emission, is of great concern as the EUexamines ways to meet its Kyoto Agreementcommitments. Approximately 750 million tonnesof CO2 is emitted-each year from the automotive

use of gasoline and diesel fuels in OECD Europe.Of this, it is estimated that one million tonnes isderived from the lubricant and even less(approximately 160 kilotonnes) from the lubricantadditives. Balanced against this small contributionare significant reductions in CO2 emissions fromimprovements in fuel economy achieved fromadditive-based finished lubricants. Earlier analysisshowed that the combined impact of fuel-efficiencyin engine, lubricant and additive design over thetwenty years to 1990 resulted in an annualreduction in CO2 emissions from transport by over100 million tonnes a year in OECD Europe(1990)29. This trend continues, as illustrated inFigure 26.

Chlorine

Regulators and environmental protectionorganisations have expressed concern about thechlorine content of all chemical products because ofthe potential to create dioxins when combusted.Crankcase lubricant additives marketed by ATCmember companies do not contain chlorine as adeliberately introduced functional component.Some important classes of additive componentscontain traces of chlorine as a by product ofmanufacturing processes: namely some detergents,ashless dispersants and other ashless products.However, recent studies35,36,37,38 have shown thatthe trace amounts of chlorine in commercial enginelubricants do not contribute to vehicle dioxin andfuran emissions, within the detection limits and testcapabilities currently available.

Phosphorus

The most common source of phosphorus is zincdialkyldithiophosphate (ZDDP). Typicalconcentrations in lubricants are shown in Table 9and Table 10. In response to concerns about theimpact of phosphorus on catalytic aftertreatmentsystems, phosphorus levels in lubricants have beensignificantly reduced over the last decade.

SUMMARY AND CONCLUSIONS

This paper is an update from the 1993 edition anddescribes the function and chemistry of theadditives used in automotive crankcase lubricantsfor passenger cars and trucks. The benefits provided

27

by these additives are identified and the fate of theadditives in the environment is analysed.

The additive industry continues to invest more than€100 million each year in technology developmentaimed at improved protection of automotivecrankcase and aftertreatment systems.

European market size – EU15, 2005

The European crankcase lubricants market in 2005was estimated at 2,600 kilotonnes split betweenpassenger cars (1,270 kilotonnes) and commercialvehicles (1,330 kilotonnes). This amount isapproximately 1% of fuel sold.

Lubricant additive EU15 sales data from 2005supplied by the major additive marketers have beenused to estimate the European lubricant additivemarket and to calculate typical weighted averagefinished lubricant compositions of both passengercar and commercial vehicle engine oils.

The lubricant additives market is approximately 430kilotonnes - 194 kilotonnes passenger car lubricantsand 236 kilotonnes commercial vehicle lubricants.

Fate analysis

A fate analysis of lubricants and lubricant additiveshas been carried out for both passenger car andcommercial vehicle lubricants. Crankcase lubricantsare used to fill the vehicle sump at therecommended service interval, and for top-up inbetween. Lubricants leave the engine throughlubricant consumption; down the tailpipe as gaseousemissions (combustion products or particulates),leakage through seals and gaskets during use, or indrained used oil at oil changes. Increasinglyparticulate traps are being fitted to vehicles whichalso capture ash derived from the lubricant.

For Europe, figures derived from the analysis are asfollows:

Ratio of fuel to oil burnt - 410:1

75% (326 kilotonnes) remain in the drained usedoil

24% (104 kilotonnes) is emitted in the vehicleexhaust together with fuel combustion products

The amount lost to spills and leaks is negligible

Fate of Additives – Air compartment

Regulated emissions

Lubricant additives contribute less than 1% of boththe Euro IV regulated limits and the Euro Vproposed limits for CO, NOx and HC emissions.

Lubricant additives can contribute up toapproximately 50% of the permitted particulatesemissions. Research continues to reduce particulateemissions, through development of low ashlubricants and through the use of particulate filters.

Carbon Dioxide CO2

Crankcase lubricant and lubricant additivecombustion contributes little to the greenhouse gas,carbon dioxide, in comparison to total CO2

emissions in EU-15 of 3,506 million tonnes in200639. Of this, 23% or 806 million ton CO2 isattributed to road transport40 (ref. 2). This meansthat the 0.15 million tons CO2 attributed tocrankcase additives is approximately 0.02% of thetotal CO2 emission from road transport.

Fate of additives – Drained used oil

Re-refining/reuse

Industry and government data on the use and fate ofused oils are incomplete. It is estimated that 75% (c.2,000 kilotonnes) of all crankcase oil sold, isdrained. Of this it is estimated that a quarter, 500kilotonnes, is re-refined producing lubricantbasestock. It is estimated that 1,000 kilotonnes ofused crankcase oil is burnt, saving approximately0.85 tonne of heavy fuel oil for each tonne of usedoil burnt.

Fate of additives - water and soil compartments

Calculations suggest that approximately 730kilotonnes of used crankcase oil (containing 120kilotonnes additives) is unaccounted for and couldenter the water and soil compartments.Unauthorised dumping may account for much ofthis.

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Crankcase lubricant additives undergo chemicalchange during use. Used oil contains compounds ofcalcium, magnesium, zinc and phosphorus inaddition to carbon, hydrogen, nitrogen and oxygen.Trace amounts of chlorine compounds do notcontribute to dioxin and furan emissions.

Improvements to the practices in reuse or disposalof used oils would reduce environmental impact.

Benefits

Crankcase lubricant additives provide significantbenefits to both the environment and the consumer.These include enhancing engine durability,cleanliness and friction reduction, maintaining lowexhaust emission levels and optimal fuel economyfor the vehicle. Recent lubricant development hasfocussed on ensuring compatibility with exhaustaftertreatment systems.

Lubricant additive technology enhancesperformance of base fluids derived from a variety of

crude oils. These lubricants can then be used with awide variety of fuels derived from different crudeoils and processes. Optimum use of petroleumresources is thus achieved.

Development of lubricant additive technology iscostly, requiring extensive engine testing and fieldevaluations. The additive industry spends €115million annually in Europe on new developments.Lubricant additives are engine design components,enabling the continuing evolution of engine designto provide increasingly efficient and moreenvironmentally-friendly vehicles. Lubricantadditives provide high performance engineering forthe consumer and ensure reliability, longevity andoptimal performance of the vehicle.

Lubricant additives, as a class, are lowenvironmental risk chemicals and the ATC iscommitted to ongoing health and safety reviews.

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REFERENCES

1 ATC Document 31 – An Internationally Recognised Nomenclature System for Petroleum Additives2 Henry JA; 1998 Human & Experimental Toxicology; 17; 111-1233 Lubrication, A technical publication from Texaco Inc., Vol. 76, No. 1, 1990.4 Automotive Engine Oils, A technical publication from Oronite Additive, November 1989.5 W.C. Gergel, Lubricant Additive Chemistry, presented at the International symposium Technical OrganicAdditives and Environment, Interlaken Switzerland, May 24-25,1984.6 Additives For Lubricants, Basic Lubrication Course STLE 1991 Education programme.7 Ph. Duteurtre, J. Goes, Cl. Orsi, G. Pam, A. Rossi, Lubrification Facteur de Progrès, Pétrole et Technique,November 1989, No. 35 1.8 Les Huiles Pour Moteurs Automobiles, Pétrole et Technique, Mars 1991, No. 362.9 C. Gautier, Th. Gautier, J.C. Hipeaux, M. Thebauld, L’huile moteur: un produit technique.10 D. Humbert, C. Orsi, Ph. Duteurtre, Peut-on Concilier les Exigences Americaines et Européennes en Matierde Lubrifiant pour Moteur Diesel - Ingénieurs de l’automobile, spécial Diesel 1987.11 A. Schilling, Les Huiles pour Moteur et le Graissage des Moteurs, Tome 1, 1975.12 The Lubricants Business, Shell Briefing Service (SBS) No. 6 - 1987.13 11. S. Q. Rizvi, Lubricant Additives, in R.J. Blau, ed., Friction, Lubrication and Wear Technology ASMPress, 1992.14 M. Rasberger in "Chemistry and Technology of Lubricants", Editors Mortier & Orszulik, 2nd edition 1997,Chapter 415 ATC Document 52 – Fuel Additives and the Environment16 AID Newsletter 0614, 200617 E.D. Koerner, Alternative Fuels, The Private Carrier, 01/91, 15-20, 1991.18 N. Stern, Stern Review – The Economics of Climate Change, HM Treasury, 30 October 200619 CEC test method, document CEC L-54-9620 J. Bosse, New Developments in the Field of Lubrication, VSN - Symposium, Scheveningen, 7 March, 1991.21 RAC Vehicle Emissions Monitoring Project, November, 199022 ATC Document 86 – Fuel additive packages containing 2-EHN Best Practices manual23 Linnett et al; 1996, Technische Akadamie Esslingen24 Lubricants Additive Market in Western Europe. April 1988 Frost and Sullivan Inc. 106 Fulton St., New York,NY 1003825 Lubricating Oil Additives, November 1990. K.E. McCaleb et al. Speciality Chemicals, SRI International26 EuropaLub, EuropaLub Lubricants 2004, September 2005, www.europalub.org27 ATC Document 49, Lubricant Additives and the Environment, 199328 Collection and Disposal of Used Lubricating Oil, CONCAWE, report 5/96 November 199629 European Environment Agency Technical Report 69, Review of Selected Waste Streams: Sewage Sludge,Construction and Demolition Waste, Waste Oils, Waste from Coal Fired Power Plants and BiodegradeableMuniciple Waste, Jan 200230 Taylor Nelson Sofres Consulting, 20AW83-5 (December 2001) Critical Review of Existing and Life CycleAnalysis on the Regeneration and Incineration of Waste Oils31 Barriers to materials reclamation and recycling, Unpublished report from Warren Spring Laboratory32 Proposal for a Council Directive amending Directive 75/439/EEC on the disposal of waste oils, COM(84) 757final, ISBN 92-77-04 172-233 Unregulated Motor Vehicle Exhaust Gas Components, Volkswagen AG Research and DevelopmentPublication.34 Advanced Petroleum Based Fuels – Diesel Emission Control (APBF-DEC), Phase I Final Repost, August2003

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35 O. Hutzinger, U. Essers, H. Hagenmaier, et al, Heft R 463, Informationstagung Motoren Frühjahr 1991,Würzburg, 199136 U. Essers, O. Hutzinger, H. Hagenmaier, Untersuchungen zur Emission halogenierter Dibenzodioxine undDibenzofurane aus Verbrennungsmotoren, Forschungszentrum für Umwelt und Gesundheit, GmbH, 4/92,199237 R.K. Hewstone and G.T. Spieβ, Petroleum Review, 3/88, 61-65, 198838 Investigations on the effect of chlorine in lubricating oil and the presence of a diesel oxidation catalyst onPCDD/F releases from an internal combustion engine, Patrick H. Dyke, Mike Sutton, David Wood and JonathanMarshall, Chemosphere, Volume 67, Issue 7, April 2007, Pages 1275-128639 European Environmental Agency, EEA Technical Report 6/2006: Annual European Community GreenhouseGas Inventory 1990-2004 and Inventory Report 200640 The value of 806 million tons CO2 from road transport compares very well to the value of 800 million tonbased on converting 260 million tons of fuel to CO2