CN105713703B

CN105713703B - Marine engine lubrication

Info

Publication number: CN105713703B
Application number: CN201510957584.6A
Authority: CN
Inventors: J·C·多德; A·索耶; J·V·辛普金斯; J·H·斯迈思
Original assignee: Infineum International Ltd
Current assignee: Infineum International Ltd
Priority date: 2014-12-19
Filing date: 2015-12-18
Publication date: 2020-05-15
Anticipated expiration: 2035-12-18
Also published as: CN105713703A; EP3034587A1; ES2759077T3; AU2015271928B2; SG10201510456QA; CA2915701C; CA2915701A1; EP3034587B1; JP2016117900A; AU2015271928A1; KR20160075361A

Abstract

Barrel piston marine engine crankcase lubrication is carried out by a composition including a nitrogen-containing ashless dispersant additive component in an amount to provide 50 to 150 ppm N by mass to reduce BN loss and reduce viscosity increase during use of the composition without adversely affecting deposit performance.

Description

Marine engine lubrication

Technical Field

The present invention relates to the lubrication of a 4-stroke marine diesel internal combustion engine (commonly referred to as a trunk piston engine). The lubricant used is commonly referred to as trunk piston engine oil ("TPEO").

Background

Trunk piston engines may be used in marine, power generation, and railroad traction applications and may have higher speeds than crosshead engines. A single lubricant (TPEO) is used for crankcase and cylinder lubrication. All major moving parts of the engine, i.e. the main and big end bearings, the camshaft and the valve gear, are lubricated by the pumping circulation system. The cylinder liner is lubricated partly by splash lubrication and partly by oil from the circulation system, which reaches the cylinder wall through the bore in the piston skirt via the connecting rod and the piston pin. Trunk piston engines typically include a centrifuge to clean the TPEO.

Nitrogen-containing ashless dispersants are known in the art as additives to TPEO. See, for example, EP-A-2133740; US-A-2009/0203559; US-A-2009/0011966; EP-A-1528099 and EP-A-1209218.

However, the effect of nitrogen-containing ashless dispersants on Base Number (BN) reduction (dilution) during TPEO use is not addressed in the art; nor does it mention its effect on viscosity increase.

Disclosure of Invention

It has now been found that the use of nitrogen-containing ashless dispersants in TPEO in defined amounts has a beneficial effect on BN and viscosity without adversely affecting deposit performance.

Accordingly, the present invention provides the use of a nitrogen-containing ashless dispersant additive in an amount to provide 50 to 150, preferably 75 to 125, mass ppm N in a trunk piston marine lubricating oil composition for a medium speed compression-ignited marine engine fuelled with and lubricated by a heavy fuel oil, said composition having a BN of 20 to 60, preferably 30 to 55, to reduce BN losses and reduce viscosity increase without adversely affecting deposit properties, preferably as compared to similar applications when the amount of nitrogen-containing ashless dispersant is outside of the above ranges.

In the present specification, the following words and expressions (if and when used) have the meanings given below:

"active ingredient" or "(a.i.)" means an additive material that is not a diluent or solvent;

"comprises" or any equivalent language indicates the presence of the stated features, steps, or integers or components but does not preclude the presence or addition of one or more other features, steps, integers, components or groups thereof; the expression "consisting of or" consisting essentially of or the like may be included within the expression "comprising" or the like, wherein "consisting essentially of allows the inclusion of substances that do not materially affect the characteristics of the composition in which they are used;

"major amount" means 50 mass% or more, preferably 60 mass% or more, even more preferably 60 mass% or more, most preferably 70 mass% or more of the composition;

"minor amount" means less than 50 mass%, preferably less than 40 mass%, even more preferably less than 30 mass%, most preferably less than 20 mass% of the composition;

"TBN" means the total base number as measured by ASTM D2896, and "BN" has the same meaning.

In addition, in the present specification, if and when used:

"calcium content" is measured by ASTM 4951;

"phosphorus content" is measured by ASTM D5185;

"sulfated ash content" is measured by ASTM D874;

"sulfur content" is measured by ASTM D2622;

"KV 100" refers to the kinematic viscosity at 100 ℃ as measured by ASTM D445.

Furthermore, it is to be understood that the various components used (basic as well as best and commonly used components) may be reacted under conditions of formulation, storage or use, and that the invention also provides products obtainable or obtained from any such reaction.

Further, it should be understood that any of the upper and lower amounts, ranges and ratios given herein may be independently combined.

Detailed Description

The features of the present invention will be discussed in more detail below.

Lubricant composition for trunk piston marine engine ('TPEO')

TPEO can use 7 to 35 mass%, preferably 10 to 28 mass%, more preferably 12 to 24 mass% of the concentrate or additive package, the remainder being base stock (oil of lubricating viscosity). Preferably, TPEO has a composition TBN (using D2896) of from 20 to 60, preferably from 25 or from 30 to 55.

The following may be mentioned as typical proportions of additives in TPEO.

When multiple additives are used, it may be desirable, but not necessary, to prepare one or more additive packages or concentrates comprising the additives whereby the multiple additives can be added simultaneously to an oil of lubricating viscosity to form a lubricating oil composition. Dissolution of the additive package in the lubricating oil may be facilitated by the solvent and by agitation with mild heating, but this is not essential. The additive package is typically formulated to contain the additives in appropriate amounts to provide the desired concentrations, and/or to perform the intended function in the final formulation when the additive package is combined with a predetermined amount of base lubricant. Thus, the additive according to the invention can be blended with a small amount of base oil or other compatible solvent and other desired additives to form an additive package comprising active ingredients in an amount of, for example, 2.5 to 90 mass%, preferably 5 to 75 mass%, most preferably 8 to 60 mass% of suitably proportioned additives based on the additive package, the remainder being base oil.

Nitrogen-containing ashless dispersant

Dispersants are additives to lubricating compositions and their primary function is to keep solid and liquid contaminants in suspension, thereby deactivating them and reducing engine deposits while reducing sludge deposits. Thus, for example, dispersants maintain in suspension oil-insoluble materials produced by oxidation during use of the lubricant, thereby preventing sludge flocculation and precipitation or deposition on metal parts of the engine.

By "ashless" is meant that the dispersant is a non-metallic organic material which, unlike a metal-containing, and therefore ash-forming, material, does not substantially form ash on combustion. Ashless dispersants comprise long chain hydrocarbons having a polar head derived from inclusion of, for example, O, P or an N atom, in the present invention, an N atom. The hydrocarbon is a lipophilic group that imparts solubility to the oil, having, for example, 40 to 500 carbon atoms. Thus, ashless dispersants may comprise an oil-soluble polymeric hydrocarbon backbone having functional groups capable of associating with the particles to be dispersed. Typically, the dispersant comprises an amine, alcohol, amide or ester polar moiety attached to the polymer backbone, typically via a bridging group. The ashless dispersant may, for example, be selected from oil-soluble salts, esters, amino esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono-and dicarboxylic acids or their anhydrides; thiocarboxylate derivatives of long chain hydrocarbons; a long chain aliphatic hydrocarbon having a polyamine attached directly thereto; and Mannich reaction products formed by condensing long chain substituted phenols with formaldehyde and polyalkylene polyamines, such as those described in U.S. Pat. No. 3,442,808.

The oil-soluble polymeric hydrocarbon backbone is typically an olefin polymer or polyene, particularly comprising a major molar amount (i.e., greater than 50 mol%) of C₂-C₁₈Olefins (e.g., ethylene, propylene, butene, isobutene, pentene, octene-1, styrene), usually C₂-C₅Polymers of olefins. The oil-soluble polymeric hydrocarbon backbone may be a homopolymer (e.g., polypropylene or polyisobutylene) or two or more such olefinsOther copolymers include those in which a minor molar amount of the copolymer monomer, e.g., 1 to 10 mol%, is α omega-diene, such as C₃-C₂₂Non-conjugated dienes (e.g., a copolymer of isobutylene and butadiene, or a copolymer of ethylene, propylene and 1, 4-hexadiene or 5-ethylidene-norbornene). Atactic propylene oligomers, which usually have an Mn of 700-5000, as described in EP-A-490454, and heteropolymers, such as polyepoxides, can also be used.

A preferred class of olefin polymers is polybutene, especially Polyisobutylene (PIB) or poly-n-butene, which may be polymerized, for example, by C₄Another preferred class of olefin polymers are ethylene α -olefin (EAO) copolymers and are of high in each case (e.g., those prepared by polymerization of refinery streams)>30%) α -olefin homo-and copolymers with terminal vinylidene unsaturation, such as those described in WO-94/13709, which can be functionalized and aminated to obtain dispersants.

Dispersants include, for example, derivatives of long chain hydrocarbon-substituted carboxylic acids, examples being derivatives of high molecular weight hydrocarbyl-substituted succinic acids. One group of dispersants of note are hydrocarbon-substituted succinimides prepared, for example, by reacting the above-mentioned acids (or derivatives) with nitrogen-containing compounds, advantageously polyalkylene polyamines, such as polyethylene polyamines. Preferably, the hydrocarbyl group is a polyalkenyl group. Such polyalkenyl (e.g., polybutenyl) moieties can have a number average molecular weight of 200-3000, preferably 350-1000, more preferably 400-960, or 400-950. Particularly preferred are the reaction products of polyalkylene polyamines with alkenyl succinic anhydrides, such as US-A-3,202,678; -3,154,560; -3,172,892; -3,024,195; -3,024,237; 3,219,666 and-3,216,936 and BE-A66,875, which may BE post-treated to improve their properties, for example boration (as described in US-A-3,087,936 and-3,254,025); fluorination and oxylation. Boration may be achieved, for example, by treating the acyl nitrogen-containing dispersant with a boron compound selected from the group consisting of boron oxide, boron halides, boric acid, and boric acid-containing esters.

As stated, the dispersant provides 50 to 150 mass ppm N atoms to the TPEO.

The coadditives will now be described in more detail.

Metal detergent

Detergents are additives that reduce the formation of deposits in engines, such as high temperature varnish and lacquer deposits; it has acid neutralizing properties and is capable of keeping finely divided solids in suspension. It is based on metal "soaps", i.e. metal salts of acidic organic compounds, sometimes referred to as surfactants.

Detergents comprise a polar head with a long hydrophobic tail. A large amount of metal base is included by reacting an excess of a metal compound, such as an oxide or hydroxide, with an acidic gas, such as carbon dioxide, to give an overbased detergent comprising neutral and detergent as the outer layer of a metal base (e.g. carbonate) micelle.

The detergent is preferably an overbased oil-soluble or oil-dispersible calcium, magnesium, sodium or barium salt of an alkali metal or alkaline earth metal additive, such as a surfactant selected from the group consisting of phenol, sulphonic acid, carboxylic acid, salicylic acid and naphthenic acid, wherein the overbasing is provided by an oil-insoluble salt of the metal, such as a carbonate, basic carbonate, acetate, formate, hydroxide or oxalate, which is stabilised by an oil-soluble salt of the surfactant. The metal of the oil-soluble surfactant salt may be the same as or different from the metal of the oil-insoluble salt. Preferably, the metal, whether an oil-soluble or oil-insoluble salt, is calcium.

The TBN of the detergent may be low, i.e., less than 50mg KOH/g; medium, i.e., 50-150mg KOH/g; or high, i.e., greater than 150mg KOH/g, TBN as determined by ASTM D2896. Preferably, the TBN is medium or high, i.e. 50TBN or more. More preferably, the TBN as determined by ASTM D2896 is at least 60, more preferably at least 100, more preferably at least 150, up to 500, for example up to 350mg KOH/g.

Preferably, the detergent comprises an alkaline earth salt of a hydrocarbyl-substituted hydroxybenzoic acid, for example a calcium alkyl salicylate salt.

The terms "oil-soluble" or "oil-dispersible" as used herein do not necessarily mean that the compound or additive may be soluble, dissolvable, miscible in all proportions, or capable of being suspended in an oil. However, these terms actually mean that they are, for example, soluble or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is used. Furthermore, additional incorporation of other additives may also allow for the incorporation of higher levels of a particular additive, if desired.

The lubricant compositions of the present invention comprise defined individual (i.e., individual) components that may or may not remain chemically the same before and after mixing.

Other Co-additives

The lubricating oil composition of the present invention may contain other additives. Such additional additives may, for example, include other metal detergents, antiwear agents, for example, ZDDP, antioxidants such as amine or phenol antioxidants, and demulsifiers.

Oil of lubricating viscosity

The lubricating oil present as the major proportion of TPEO may range in viscosity from light distillate mineral oils to heavy lubricating oils. Generally, the viscosity of the oil measured at 100 ℃ ranges from 2 to 40mm²/sec。

Natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil); liquid petroleum oils and hydrotreated, solvent-treated or acid-treated mineral oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils.

Synthetic lubricating oils include hydrocarbon oils and halogenated hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly (1-hexenes), poly (1-octenes), poly (1-decenes)); alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di- (2-ethylhexyl) benzene); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof.

Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified, e.g. by esterification or etherification, constitute another class of knownSynthesizing the lubricating oil. Examples thereof include polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having a molecular weight of 1000 or diphenyl ether of polyethylene glycol having a molecular weight of 1000-1500); and mono-and polycarboxylic esters thereof (e.g. acetates, mixed C)₃-C₈C of fatty acid ester and tetraethylene glycol₁₃A diester of an oxo acid.

Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Specific examples of such esters include dibutyl adipate, di (2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and complex esters formed by reacting 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid.

Esters useful as synthetic oils also include those made from C₅-C₁₂Monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.

Silicon-based oils such as polyalkyl, polyaryl, polyalkoxy or polyaryloxy silicone oils and silicate oils constitute another useful class of synthetic lubricants; such oils include tetraethyl silicate, tetraisopropyl silicate, tetra- (2-ethylhexyl) silicate, tetra- (4-methyl-2-ethylhexyl) silicate, tetra- (p-tert-butylphenyl) silicate, hexa- (4-methyl-2-ethylhexyl) disiloxane, poly (methyl) siloxanes and poly (methylphenyl) siloxanes. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans.

Unrefined, refined and rerefined oils are useful in the lubricants of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, shale oil obtained directly from retorting operations, petroleum oil obtained directly from distillation, or ester oil obtained directly from esterification processes used without further treatment are unrefined oils. Refined oils are similar to unrefined oils except that the oil is further treated in one or more purification steps to improve one or more properties. Many such purification techniques, such as distillation, solvent extraction, acid or base extraction, filtration and diafiltration, are known to those skilled in the art. Rerefined oils are obtained by processes similar to those used to provide refined oils, but starting with oils that have been used in service. These rerefined oils are also known as reclaimed or reprocessed oils and often undergo additional processing using techniques directed to removal of spent additives and oil breakdown products.

The American Petroleum Institute (API) publication "Engine Oil Licensing and certification System", Industry Service Department, fourteenth edition, 12 months 1996, appendix 1, 12 months 1998 classifies the base stocks as follows:

a) group I base stocks contain less than 90% saturates and/or greater than 0.03% sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in the table below.

b) The second base stock comprises greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and has a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in the table below.

c) Group III basestocks contain greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and have a viscosity index greater than or equal to 120 using the test methods specified in the tables below.

d) Group IV basestocks are polyal-olefins (PAO).

e) Group V base stocks include all other base stocks not included in group I, II, III or IV.

The analytical test methods for the above-mentioned base stocks are given in the following table:

performance of	Test method
		Saturates	ASTM D 2007
Viscosity index	ASTM D 2270
		Sulfur	ASTM D 2622
	ASTM D 4294
			ASTM D 4927
	ASTM D 3120

As examples of the above oils, mention may be made of group I and group II oils. Furthermore, as oils of lubricating viscosity, mention may be made of those containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur in the above-mentioned oils, for example of group II, III, IV or V. They also include base stocks derived from hydrocarbons synthesized by the fischer-tropsch process. In the fischer-tropsch process, a synthesis gas (or "syngas") is first produced comprising carbon monoxide and hydrogen, and then converted to hydrocarbons using a fischer-tropsch catalyst. These hydrocarbons generally require further processing in order to be useful as base oils. For example, they may be hydroisomerized, by methods known in the art; hydrocracking and hydroisomerization; dewaxing; or hydroisomerization and dewaxing. Syngas may be produced, for example, from a gas such as natural gas or other gaseous hydrocarbons by steam reforming, in which case the base stock may be referred to as a gas-to-liquid ("GTL") base oil; or syngas can be produced, for example, from gasification of biomass, in which case the base stock can be referred to as biomass-to-liquid ("BTL" or "BMTL") base oil; or syngas can be produced, for example, from the gasification of coal, in which case the base stock can be referred to as coal-to-liquid ("CTL") base oil.

Preferably, the oil of lubricating viscosity in the present invention contains 50 mass% or more of the base stock. It may contain 60, for example 70, 80 or 90 mass% or more of the base stock or mixture thereof. The oil of lubricating viscosity may be substantially all of the base stock or a mixture thereof.

It may be desirable, but not necessary, to prepare one or more additive packages or concentrates comprising additives whereby the additives may be added simultaneously to the oil of lubricating viscosity to form TPEO.

The final formulation as a trunk piston engine oil may typically contain 30, preferably 10 to 28, more preferably 12 to 24 mass% of the additive package, the remainder being oil of lubricating viscosity. Preferably, the trunk piston engine oil may have a composition TBN (using ASTM D2896) of 20-60, for example 30-55. For example, it may be 40-55 or 35-50.

The treat rate (treat rate) of the additive contained in the lubricating oil composition may be, for example, in the range of 1 to 2.5, preferably 2 to 20, more preferably 5 to 18 mass%.

Examples

The invention is illustrated by the following examples, without being limited thereto.

Cylinder piston engine oil (TPEO)

A set of TPEOs was formulated comprising two TPEOs differing only in that one contained a nitrogen-containing ashless dispersant and the other did not. Each TPEO contains a mixture of overbased calcium salicylate detergents, a mixture of amine and phenolic antioxidants, and other co-additives. They contain the same base oil making up the remainder. The dispersant was a product of reacting polyisobutenyl succinic anhydride with tetraethylene pentamine, and provided 91 mass ppm of N to TPEO. The polyisobutenyl moiety has a number average molecular weight of 950.

Each TPEO was tested in a bulk oil oxidation test in which the oil was contaminated with 0.5% HFO (heavy fuel oil) and subjected to oxidation conditions for 120 hours. The test is a DKA oxidation test (CEC L-48-00) in which BN and viscosity change are evaluated.

Each TPEO was also tested in a panel scorch test, as described below:

coking test of painted plate

Lubricating oils can degrade on hot engine surfaces and leave deposits that will affect engine performance; the panel coking test simulates typical conditions and measures the tendency of oil to form such deposits. The oil tested was splashed onto a hot metal plate by rotating a metal comb-shaped splash device in a sump containing the oil. At the end of the test period, the deposits were measured.

The summary of the test methods is as follows:

225ml of the oil was heated to 100 ℃ in an oil bath.

A hot aluminum plate was placed in an inclined state above the oil bath, and maintained at a temperature of 320 ℃.

The oil was sputtered against the plate for 15 seconds followed by 45 seconds without sputtering.

This cycle of intermittent sputtering lasts 1 hour.

Weigh the panel and calculate the deposit, grams (g).

Fresh oil (without HFO) and doping oil (with 2.5% HFO) were tested. Results are presented on a scale of 1-10, where lower values indicate poorer deposit performance.

The results are tabulated below, with the example without dispersant being referred to as "Ref" and the example with dispersant being referred to as "Inv".

The results show that the inventive example (Inv) containing a dispersant shows both a lower reduction in BN and a lower increase in KV100 compared to the comparative example (Ref). Furthermore, the results show that when a small amount of dispersant is present, the deposit cleanliness in the paint-forming panel coking test is significantly improved, even when TPEO is contaminated with 2.5% HFO.

Claims

1. Use of a nitrogen-containing ashless dispersant additive in an amount to provide 50 to 150 ppm by mass N in a trunk piston marine lubricating oil composition for a medium speed compression-ignited marine engine fuelled with and lubricated by a heavy fuel oil, said composition having a BN of 20 to 60, to reduce BN losses and reduce viscosity increase without adversely affecting deposit properties, wherein

The dispersant is a hydrocarbyl-substituted succinimide, and

the compositions contain an overbased calcium alkyl-substituted hydroxybenzoate detergent additive.

2. The use according to claim 1, wherein the use is to reduce BN loss and reduce viscosity increase without adversely affecting deposit performance as compared to similar applications when the amount of nitrogen-containing ashless dispersant is outside the above range.

3. Use according to claim 1 or 2, wherein the nitrogen-containing ashless dispersant additive is used in an amount to provide 75 to 125 mass ppmN in a lubricating oil composition for piston bowl ships.

4. Use according to claim 1 or 2, wherein the composition has a BN of 30-55.

5. The use of claim 1 or 2, wherein the composition comprises a major amount of an oil of lubricating viscosity containing 50 mass% or more of a base stock containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur.

6. The use of claim 3, wherein the composition comprises a major amount of an oil of lubricating viscosity containing 50 mass% or more of a base stock containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur.

7. The use of claim 4, wherein the composition comprises a major amount of an oil of lubricating viscosity containing 50 mass% or more of a base stock containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur.

8. The use of claim 1, 2,6 or 7 wherein the overbased calcium alkyl-substituted hydroxybenzoate detergent additive is a calcium salicylate detergent.

9. The use of claim 3, wherein the overbased calcium alkyl-substituted hydroxybenzoate detergent additive is a calcium salicylate detergent.

10. The use of claim 4, wherein the overbased calcium alkyl-substituted hydroxybenzoate detergent additive is a calcium salicylate detergent.

11. The use of claim 5, wherein the overbased calcium alkyl-substituted hydroxybenzoate detergent additive is a calcium salicylate detergent.

12. Use according to any one of claims 1, 2,6, 7 and 9 to 11, wherein the composition contains one or more co-additives selected from aminic or phenolic antioxidants and from ashless dispersants.

13. Use according to claim 3, wherein the composition contains one or more co-additives selected from aminic or phenolic antioxidants and from ashless dispersants.

14. Use according to claim 4, wherein the composition contains one or more co-additives selected from aminic or phenolic antioxidants and from ashless dispersants.

15. Use according to claim 5, wherein the composition contains one or more co-additives selected from aminic or phenolic antioxidants and from ashless dispersants.

16. Use according to claim 8, wherein the composition contains one or more co-additives selected from aminic or phenolic antioxidants and from ashless dispersants.

17. The use of any one of claims 1, 2,6, 7, 9-11 and 13-16, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

18. The use of claim 3, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

19. The use of claim 4, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

20. The use of claim 5, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

21. The use of claim 8, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

22. The use of claim 12, wherein the dispersant is a hydrocarbyl-substituted succinimide derived from a polyalkylene polyamine.

23. The use as claimed in claim 17, wherein the hydrocarbyl group is a polyisobutenyl moiety having a number average molecular weight of 400-960.

24. The use as claimed in any one of claims 18 to 22 wherein the hydrocarbyl group is a polyisobutenyl moiety having a number average molecular weight of 400 and 960.