AU2010234300B2

AU2010234300B2 - Marine engine lubrication

Info

Publication number: AU2010234300B2
Application number: AU2010234300A
Authority: AU
Inventors: Terry Garner; Laura Gregory; Joseph Hartley; Peter Watts
Original assignee: Infineum International Ltd
Current assignee: Infineum International Ltd
Priority date: 2009-04-07
Filing date: 2010-03-31
Publication date: 2014-04-24
Anticipated expiration: 2030-03-31
Also published as: CA2755308A1; KR101662350B1; US20120028522A1; KR101654397B1; CA2755815A1; AU2010234300A1; KR20120027208A; EP2417234A1; WO2010115595A9; CA2755815C; SG174925A1; EP2417234B1; WO2010115595A1; KR20120006995A; CN102365352A; CN104277894A; US20120028521A1; WO2010115594A9; JP5698728B2; EP2417233A1

Abstract

Trunk piston marine engine lubrication, when the engine is fueled by heavy fuel oil, is effected by a composition comprising a major amount of an oil of lubricating viscosity containing at least 50 mass % of a Group II basestock, and respective minor amounts of an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent other than such a detergent having a basicity index of less than two and a degree of carbonation of 80% or greater and at least 1 mass % of a hydrocarbyl-substituted carboxylic acid, anhydride, ester or amide thereof. Asphaltene precipitation in the lubricant, caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

Description

WO 2010/115595 1 PCT/EP2010/002132 MARINE ENGINE LUBRICATION FIELD OF THE INVENTION This invention relates to a trunk piston marine engine lubricating composition for a medium-speed four-stroke compression-ignited (diesel) marine engine and lubrication of such an engine. BACKGROUND OF THE INVENTION Marine trunk piston engines generally use Heavy Fuel Oil ('HFO') for offshore running. Heavy Fuel Oil is the heaviest fraction of petroleum distillate and comprises a complex mixture of molecules including up to 15% of asphaltenes, defined as the fraction of petroleum distillate that is insoluble in an excess of aliphatic hydrocarbon (e.g. heptane) but which is soluble in aromatic solvents (e.g. toluene). Asphaltenes can enter the engine lubricant as contaminants either via the cylinder or the fuel pumps and injectors, and asphaltene precipitation can then occur, manifested in 'black paint' or 'black sludge' in the engine. The presence of such carbonaceous deposits on a piston surface can act as an insulating layer which can result in the formation of cracks that then propagate through the piston. If a crack travels through the piston, hot combustion gases can enter the crankcase, possibly resulting in a crankcase explosion. It is therefore highly desirable that trunk piston engine oils ('TPEO's) prevent or inhibit asphaltene precipitation. The prior art describes ways of doing this. WO 96/26995 discloses the use of a hydrocarbyl-substituted phenol to reduce 'black paint' in a diesel engine. WO 96/26996 discloses the use of a demulsifier for water-in-oil emulsions, for example, a polyoxyalkylene polyol, to reduce 'black paint' in diesel engines. US-B2-7,053,027 describes use of one or more overbased metal carboxylate detergents in combination with an antiwear additive in a dispersant-free TPEO. The problem of asphaltene precipitation is more acute at higher basestock saturate levels. WO 2008/128656 describes a solution by use of an overbased metal hydrocarbyl substituted hydroxybenzoate detergent having a basicity index of less than 2 and a degree of WO 2010/115595 PCT/EP2010/002132 carbonation of 80% or greater in a marine trunk piston engine lubricant to reduce asphaltene precipitation in the lubricant. Exemplified are lubricants comprising a Group II basestock, which has a higher basestock saturate level than a Group I basestock. The above-described solution is however restricted to a specific class of detergents. It is now found, in the present invention, that the problem in WO 2008/128656 is solved for a different range of overbased metal carboxylate detergents by employing, in combination therewith, a hydrocarbyl-substituted carboxylic acid, anhydride, ester or amide in Group II basestocks. SUMMARY OF THE INVENTION A first aspect of the invention is a trunk piston marine engine lubricating oil composition for improving asphaltene handling in use thereof, in operation of the engine when fuelled by a heavy fuel oil, which composition comprises or is made by admixing an oil of lubricating viscosity, in a major amount, containing 50 mass % or more of a Group II basestock, and, in respective minor amounts: (A) an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent other than such a detergent having a basicity index of less than two and a degree of carbonation of 80% or greater, where degree of carbonation is the percentage of carbonate present in the overbased metal hydrocarbyl-substituted hydroxybenzoate detergent expressed as a mole percentage relative to the total excess base in the detergent; and (B) a hydrocarbyl-substituted carboxylic acid, anhydride, ester or amide thereof, wherein the or at least one hydrocarbyl group contains at least eight carbon atoms, the acid, anhydride, ester or amide constituting at least 1 mass % of the lubricating oil composition. A second aspect of the invention is the use of a detergent (A) in combination with a carboxylic acid, anhydride, ester or amide (B) as defined in, and in the amounts stated in, the first aspect of the invention in a trunk piston marine lubricating oil composition for a medium speed compression-ignited marine engine, which composition comprises an oil of lubricating WO 2010/115595 PCTIEP2010/002132 viscosity in a major amount and contains 50 mass % or more of a Group II basestock, to improve asphaltene handling during operation of the engine, fueled by a heavy fuel oil, and its lubrication by the composition, in comparison with analogous operation when the same amount of detergent (A) is used in the absence of (B). A third aspect of the invention is a method of operating a trunk piston medium-speed compression-ignited marine engine comprising (i) fueling the engine with a heavy fuel oil; and (ii) lubricating the crankcase of the engine with a composition as defined in the first aspect of the invention. A fourth aspect of the invention is a method of dispersing asphaltenes in a trunk piston marine lubricating oil composition during its lubrication of surfaces of the combustion chamber of a medium-speed compression-ignited marine engine and operation of the engine, which method comprises (i) providing a composition as defined in the first aspect of the invention; (ii) providing the composition in the combustion chamber; (iii) providing heavy fuel oil in the combustion chamber; and (iv) combusting the heavy fuel oil in the combustion chamber. In this specification, the following words and expressions, if and when used, have the meanings ascribed below: "active ingredients" or "(a.i.)" refers to additive material that is not diluent or solvent; "comprising" or any cognate word specifies the presence of 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 expressions 4 "consists of or "consists essentially of or cognates may be embraced within "comprises" or cognates, wherein "consists essentially of' permits inclusion of substances not materially affecting the characteristics of the composition to which it applies; 5 "major amount" means in excess of 50 mass % of a composition; "minor amount" means less than 50 mass % of a composition; 10 "TBN" means total base number as measured by ASTM D2896. Furthermore in this specification: "calcium content" is as measured by ASTM 4951; 15 "phosphorus content" is as measured by ASTM D5185; "sulphated ash content" is as measured by ASTM D874; 20 "sulphur content" is as measured by ASTM D2622; "KV1 00" means kinematic viscosity at 100 C as measured by ASTM D445. Also, it will be understood that various components used, essential as well 25 as optimal and customary, may react under conditions of formulation, storage or use and that the invention also provides the product obtainable or obtained as a result of any such reaction. Further, it is understood that any upper and lower quantity, range and ratio 30 limits set forth herein may be independently combined. An aspect of the present invention provides a trunk piston marine engine lubricating oil composition for improving asphaltene handling in use thereof, in 4a operation of the engine when fuelled by a heavy fuel oil, which composition includes or is made by admixing an oil of lubricating viscosity, in a major amount, containing 50 mass % or more of a Group Il basestock, and, in respective minor amounts: 5 (A) an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent other than such a detergent having a basicity index of less than two and a degree of carbonation of 80% or greater, where degree of carbonation is the percentage of carbonate present in the overbased metal hydrocarbyl 10 substituted hydroxybenzoate detergent expressed as a mole percentage relative to the total excess base in the detergent; and (B) a hydrocarbyl-substituted carboxylic acid or anhydride thereof, wherein the or at least one hydrocarbyl group contains at least eight carbon atoms, the 15 acid or anhydride constituting at least 1 and up to 10 mass % of the lubricating oil composition.

WO 2010/115595 PCT/EP2010/002132 DETAILED DESCRIPTION OF THE INVENTION The features of the invention will now be discussed in more detail below. OIL OF LUBRICATING VISCOSITY The lubricating oils may range in viscosity from light distillate mineral oils to heavy lubricating oils. Generally, the viscosity of the oil ranges from 2 to 40 mm2/sec, as measured at 100 0 C. Natural oils include animal oils and vegetable oils (e.g., caster oil, lard oil); liquid petroleum oils and hydrorefined, 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 also serve as useful base oils. Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1 octenes), poly(I-decenes)); alkybenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulphides and derivative, analogs and homologs thereof. Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc., constitute another class of known synthetic lubricating oils. These are exemplified by polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol ether having a molecular weight of 1000 or diphenyl ether of poly-ethylene glycol having a molecular weight of 1000 to 1500); and mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C 3

-C

8 fatty acid esters and C 13 Oxo acid diester of tetraethylene glycol. 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 WO 2010/115595 PCT/EP2010/002132 acid, azelaic acid, suberic acid, sebasic 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 includes 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 the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid. Esters useful as synthetic oils also include those made from C 5 to C 12 monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol. Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxysilicone oils and silicate oils comprise 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-butyl-phenyl) silicate, hexa-(4-methyl-2 ethylhexyl)disiloxane, poly(methyl)si loxanes and poly(methylphenyl)siloxanes. Other synthetic lubricating oils include liquid esters of phosphorous-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans. Unrefined, refined and re-refined oils can be used in lubricants of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations; petroleum oil obtained directly from distillation; or ester oil obtained directly from an esterification and used without further treatment would be an unrefined oil. 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 percolation are known to those skilled in the art. Re-refined oils are obtained by processes similar to those used to provide refined oils but begin with oil that has already been used in service. Such re-refined oils are also known as reclaimed or reprocessed oils and are often subjected to additional processing using techniques for removing spent additives and oil breakdown products.

WO 2010/115595 PCTIEP2010/002132 Definitions for the base stocks and base oils in this invention are the same as those found in the American Petroleum Institute (API) publication "Engine Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998. Said publication categorizes base stocks as follows: a) Group I base stocks contain less than 90 percent saturates and/or greater than 0.03 percent sulphur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table E-1. b) Group II base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulphur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table E-1. c) Group III base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulphur and have a viscosity index greater than or equal to 120 using the test methods specified in Table E-1. d) Group IV base stocks are polyalphaolefins (PAO). e) Group V base stocks include all other base stocks not included in Group I, II, III, or IV. Analytical Methods for Base Stock are tabulated below: PROPERTY TEST METHOD Saturates ASTM D 2007 Viscosity Index ASTM D 2270 Sulphur ASTM D 2622 ASTM D 4294 ASTM D 4927 ASTM D 3120 As stated, the oil of lubricating viscosity in this invention contains 50 mass % or more of a Group II basestock. Preferably, it contains 60, such as 70, 80 or 90, mass % or more of a WO 2010/115595 PCTIEP2010/002132 Group II basestock. The oil of lubricating viscosity may be substantially all Group II basestock. OVERBASED METAL DETERGENT (A) A metal detergent is an additive based on so-called metal "soaps", that is metal salts of acidic organic compounds, sometimes referred to as surfactants. They generally comprise a polar head with a long hydrophobic tail. Overbased metal detergents, which comprise neutralized metal detergents as the outer layer of a metal base (e.g. carbonate) micelle, may be provided by including large amounts of metal base by reacting an excess of a metal base, such as an oxide or hydroxide, with an acidic gas such as carbon dioxide. In the present invention, overbased metal detergents (A) are overbased metal hydrocarbyl-substituted hydroxybenzoate, preferably h ydrocarbyl-substituted salicylate, detergents. "Hydrocarbyl" means a group or radical that contains carbon and hydrogen atoms and that is bonded to the remainder of the molecule via a carbon atom. It may contain hetero atoms, i.e. atoms other than carbon and hydrogen, provided they do not alter the essentially hydrocarbon nature and characteristics of the group. As examples of hydrocarbyl, there may be mentioned alkyl and alkenyl. The overbased metal hydrocarbyl-substituted hydroxybenzoate typically has the structure shown: OH Om R wherein R is a linear or branched aliphatic hydrocarbyl group, and more preferably an alkyl group, including straight- or branched-chain alkyl groups. There may be more than one R group attached to the benzene ring. M is an alkali metal (e.g. lithium, sodium or potassium) or alkaline earth metal (e.g. calcium, magnesium barium or strontium). Calcium or magnesium is preferred; calcium is especially preferred. The COOM group can be in the ortho, meta or para position with respect to the hydroxyl group; the ortho position is preferred. The R group can be in the ortho, meta or para position with respect to the hydroxyl group.

WO 2010/115595 PCT/EP2010/002132 Hydroxybenzoic acids are typically prepared by the carboxylation, by the Kolbe Schmitt process, of phenoxides, and in that case, will generally be obtained (normally in a diluent) in admixture with uncarboxylated phenol. Hydroxybenzoic acids may be non sulphurized or sulphurized, and may be chemically modified and/or contain additional substituents. Processes for sulphurizing a hydrocarbyl-substituted hydroxybenzoic acid are well known to those skilled in the art, and are described, for example, in US 2007/0027057. In hydrocarbyl-substituted hydroxybenzoic acids, the hydrocarbyl group is preferably alkyl (including straight- or branched-chain alkyl groups), and the alkyl groups advantageously contain 5 to 100, preferably 9 to 30, especially 14 to 24, carbon atoms. The term "overbased" is generally used to describe metal detergents in which the ratio of the number of equivalents of the metal moiety to the number of equivalents of the acid moiety is greater than one. The term 'low-based' is used to describe metal detergents in which the equivalent ratio of metal moiety to acid moiety is greater than 1, and up to about 2. By an "overbased calcium salt of surfactants" is meant an overbased detergent in which the metal cations of the oil-insoluble metal salt are essentially calcium cations. Small amounts of other cations may be present in the oil-insoluble metal salt, but typically at least 80, more typically at least 90, for example at least 95, mole %, of the cations in the oil insoluble metal salt, are calcium ions. Cations other than calcium may be derived, for example, from the use in the manufacture of the overbased detergent of a surfactant salt in which the cation is a metal other than calcium. Preferably, the metal salt of the surfactant is also calcium. Carbonated overbased metal detergents typically comprise amorphous nanoparticles. Additionally, there are disclosures of nanoparticulate materials comprising carbonate in the crystalline calcite and vaterite forms. The basicity of the detergents may be expressed as a total base number (TBN). A total base number is the amount of acid needed to neutralize all of the basicity of the overbased material. The TBN may be measured using ASTM standard D2896 or an equivalent procedure. The detergent may have a low TBN (i.e. a TBN of less than 50), a medium TBN WO 2010/115595 1u PCTIEP2010/002132 (i.e. a TBN of 50 to 150) or a high TBN (i.e. a TBN of greater than 150, such as 150-500). In this invention, Basicity Index and Degree of Carbonation may be used. Basicity Index is the molar ratio of total base to total soap in the overbased detergent. Degree of Carbonation is the percentage of carbonate present in the overbased detergent expressed as a mole percentage relative to the total excess base in the detergent. Overbased metal hydrocarbyl-substituted hydroxybenzoates can be prepared by any of the techniques employed in the art. A general method is as follows: 1. Neutralisation of hydrocarbyl-substituted hydroxybenzoic acid with a molar excess of metallic base to produce a slightly overbased metal hydrocarbyl-substituted hydroxybenzoate complex, in a solvent mixture consisting of a volatile hydrocarbon, an alcohol and water; 2. Carbonation to produce colloidally-dispersed metal carbonate followed by a post reaction period; 3. Removal of residual solids that are not colloidally dispersed; and 4. Stripping to remove process solvents. Overbased metal hydrocarbyl-substituted hydroxybenzoates can be made by either a batch or a continuous overbasing process. Metal base (e.g. metal hydroxide, metal oxide or metal alkoxide), preferably lime (calcium hydroxide), may be charged in one or more stages. The charges may be equal or may differ, as may the carbon dioxide charges which follow them. When adding a further calcium hydroxide charge, the carbon dioxide treatment of the previous stage need not be complete. As carbonation proceeds, dissolved hydroxide is converted into colloidal carbonate particles dispersed in the mixture of volatile hydrocarbon solvent and non-volatile hydrocarbon oil. Carbonation may by effected in one or more stages over a range of temperatures up to the reflux temperature of the alcohol promoters. Addition temperatures may be similar, or different, or may vary during each addition stage. Phases in which temperatures are raised, and optionally then reduced, may precede further carbonation steps.

WO 2010/115595 1 PCT/EP2010/002132 The volatile hydrocarbon solvent of the reaction mixture is preferably a normally liquid aromatic hydrocarbon having a boiling point not greater than about 150'C. Aromatic hydrocarbons have been found to offer certain benefits, e.g. improved filtration rates, and examples of suitable solvents are toluene, xylene, and ethyl benzene. The alkanol is preferably methanol although other alcohols such as ethanol can be used. Correct choice of the ratio of alkanol to hydrocarbon solvents, and the water content of the initial reaction mixture, are important to obtain the desired product. Oil may be added to the reaction mixture; if so, suitable oils include hydrocarbon oils, particularly those of mineral origin. Oils which have viscosities of 15 to 30 mm2/sec at 38'C are very suitable. After the final treatment with carbon dioxide, the reaction mixture is typically heated to an elevated temperature, e.g. above 130'C, to remove volatile materials (water and any remaining alkanol and hydrocarbon solvent). When the synthesis is complete, the raw product is hazy as a result of the presence of suspended sediments. It is clarified by, for example, filtration or centrifugation. These measures may be used before, or at an intermediate point, or after solvent removal. The products are generally used as an oil solution. If the reaction mixture contains insufficient oil to retain an oil solution after removal of the volatiles, further oil should be added. This may occur before, or at an intermediate point, or after solvent removal. In this invention, (A) may have: (Al) a basicity index of two or greater and a degree of carbonation of 80% or greater; or (A2) a basicity index of two or greater and a degree of carbonation of less than 80%; or (A3) a basicity index of less than two and a degree of carbonation of less than 80%.

WO 2010/115595 12 PCT/EP2010/002132 CARBOXYLIC ACID, ANHYDRIDE, ESTER OR AMIDE THEREOF (B) As stated, the acid, anhydride, ester or amide thereof constitutes at least 1 mass % of the lubricating oil composition. Preferably it constitutes from 1.5 such as up to 10, such as 2 to 10, for example 3 to 6, mass %. (B) may be a mixture. The acid may be mono or polycarboxylic, preferably dicarboxylic, acid. The hydrocarbyl group preferably has from 8 to 400, such as 8 to 100, carbon atoms. As (B), an anhydride of a dicarboxylic acid is preferred. Esters may be half or diesters when the acid is a dicarboxylic acid. Ester groups may include alkyl, aryl, or aralkyl, and amide groups may be unsubstituted or carry one or more alkyl, aryl or aralkyl groups. General formulae of exemplary monocarboxylic and dicarboxylic acids and anhydrides, esters or amides thereof may be depicted as

R

1 HC -COX

H

2 C- COY (I) where R' represents a C8 to Cloo branched or linear hydrocarbyl, such as a polyalkenyl, alkyl or alkaryl group; X and Y each independently represents OR 2 and OR 3 , where each R 2 and R 3 independently represents a hydrogen atom, or an alkyl, aryl or aralkyl group, or X and Y together represent -0-; and/or depicted as

R'CH

2

COR

4 (II) 4 5 6 7 5 6 7 where R represents OR 5 or NR R , where each R , R and R independently represents a hydrogen atom or an alkyl group.

WO 2010/115595 1i PCT/EP2010/002132 Preferably, the hydrocarbyl group is a polyalkenyl group. Such polyalkenyl moiety may have a number average molecular weight of from 200 to 3000, preferably from 350 to 950. Suitable hydrocarbons or polymers employed in the formation of the acid/derivative of the present invention include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C 3 to C 2 8 alpha-olefin having the formula H 2 C=CHR wherein R' is straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, preferably a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R1 is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms. Therefore, useful alpha-olefin monomers and comonomers include, for example, propylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, decene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures of propylene and butene-1, and the like). Exemplary of such polymers are propylene homopolymers, butene-1 homopolymers, ethylene-propylene copolymers, ethylene-butene-1 copolymers, propylene-butene copolymers and the like, wherein the polymer contains at least some terminal and/or internal unsaturation. Preferred polymers are unsaturated copolymers of ethylene and propylene and ethylene and butene-1. The interpolymers of this invention may contain a minor amount, e.g. 0.5 to 5 mole % of a C 4 to C18 non-conjugated diolefin comonomer. However, it is preferred that the polymers of this invention comprise only alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers and interpolymers of ethylene and alpha-olefin comonomers. The molar ethylene content of the polymers employed in this invention is preferably in the range of 0 to 80 %, and more preferably 0 to 60 %. When propylene and/or butene-1 are employed as comonomer(s) with ethylene, the ethylene content of such copolymers is most preferably between 15 and 50 %, although higher or lower ethylene contents may be present. These polymers may be prepared by polymerizing alpha-olefin monomer, or mixtures of alpha-olefin monomers, or mixtures comprising ethylene and at least one C 3 to C 28 alpha olefin monomer, in the presence of a catalyst system comprising at least one metallocene WO 2010/115595 14 PCT/EP2010/002132 (e.g., a cyclopentadienyl-transition metal compound) and an alumoxane compound. Using this process, a polymer in which 95 % or more of the polymer chains possess terminal ethenylidene-type unsaturation can be provided. The percentage of polymer chains exhibiting terminal ethenylidene unsaturation may be determined by FTIR spectroscopic analysis, titration, or C1 3 NMR. Interpolymers of this latter type may be characterized by the formula POLY-C(R1)=CH2 wherein R' is C 1 to C 26 alkyl, preferably Ci to C 18 alkyl, more preferably C, to C 8 alkyl, and most preferably C 1 to C 2 alkyl, (e.g., methyl or ethyl) and wherein POLY represents the polymer chain. The chain length of the R 1 alkyl group will vary depending on the comonomer(s) selected for use in the polymerization. A minor amount of the polymer chains can contain terminal ethenyl, i.e., vinyl, unsaturation, i.e. POLY-CH=CH2, and a portion of the polymers can contain internal monounsaturation, e.g. POLY-CH=CH(R1), wherein R1 is as defined above. These terminally unsaturated interpolymers may be prepared by known metallocene chemistry and may also be prepared as described in U.S. Patent Nos. 5,498,809; 5,663,130; 5,705,577; 5,814,715; 6,022,929 and 6,030,930. Another useful class of polymers is polymers prepared by cationic polymerization of isobutene, styrene, and the like. Common polymers from this class include polyisobutenes obtained by polymerization of a C 4 refinery stream having a butene content of about 35 to about 75 mass %, and an isobutene content of about 30 to about 60 mass %, in the presence of a Lewis acid catalyst, such as aluminum trichloride or boron trifluoride. A preferred source of monomer for making poly-n-butenes is petroleum feedstreams such as Raffinate II. These feedstocks are disclosed in the art such as in U.S. Patent No. 4,952,739. Polyisobutylene is a most preferred backbone of the present invention because it is readily available by cationic polymerization from butene streams (e.g., using AIC1 3 or BF 3 catalysts). Such polyisobutylenes generally contain residual unsaturation in amounts of about one ethylenic double bond per polymer chain, positioned along the chain. A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene olefins. Preferably, these polymers, referred to as highly reactive polyisobutylene (HR-PIB), have a terminal vinylidene content of at least 65%, e.g., 70%, more preferably at least 80%, most preferably, at least 85%. The preparation of such polymers is described, for example, in U.S. Patent No. 4,152,499. HR PIB is known and HR-PIB is commercially available under the tradenames GlissopalTM (from BASF) and UltravisTM (from BP-Amoco).

WO 2010/115595 L)U PCT/EP2010/002132 Polyisobutylene polymers that may be employed are generally based on a hydrocarbon chain of from 400 to 3000. Methods for making polyisobutylene are known. Polyisobutylene can be functionalized by halogenation (e.g. chlorination), the thermal "ene" reaction, or by free radical grafting using a catalyst (e.g. peroxide), as described below. To produce (B) the hydrocarbon or polymer backbone may be functionalized, with carboxylic acid producing moieties (acid or anhydride moieties) selectively at sites of carbon to-carbon unsaturation on the polymer or hydrocarbon chains, or randomly along chains using any of the three processes mentioned above or combinations thereof, in any sequence. Processes for reacting polymeric hydrocarbons with unsaturated carboxylic acids, anhydrides or esters and the preparation of derivatives from such compounds are disclosed in U.S. Patent Nos. 3,087,936; 3,172,892; 3,215,707; 3,231,587; 3,272,746; 3,275,554; 3,381,022; 3,442,808; 3,565,804; 3,912,764; 4,110,349; 4,234,435; 5,777,025; 5,891,953; as well as EP 0 382 450 BI; CA-1,335,895 and GB-A-1,440,219. The polymer or hydrocarbon may be functionalized, with carboxylic acid producing moieties (acid or anhydride) by reacting the polymer or hydrocarbon under conditions that result in the addition of functional moieties or agents, i.e., acid, anhydride, ester moieties, etc., onto the polymer or hydrocarbon chains primarily at sites of carbon-to-carbon unsaturation (also referred to as ethylenic or olefinic unsaturation) using the halogen assisted functionalization (e.g. chlorination) process or the thermal "ene" reaction. Selective functionalization can be accomplished by halogenating, e.g., chlorinating or brominating the unsaturated c-olefin polymer to about 1 to 8 mass %, preferably 3 to 7 mass % chlorine, or bromine, based on the weight of polymer or hydrocarbon, by passing the chlorine or bromine through the polymer at a temperature of 60 to 250'C, preferably 110 to 160 0 C, e.g., 120 to 1400C, for about 0.5 to 10, preferably 1 to 7 hours. The halogenated polymer or hydrocarbon (hereinafter backbone) is then reacted with sufficient monounsaturated reactant capable of adding the required number of functional moieties to the backbone, e.g., monounsaturated carboxylic reactant, at 100 to 250'C, usually about 180*C to 235'C, for about 0.5 to 10, e.g., 3 to 8 hours, such that the product obtained will contain the desired number of moles of the monounsaturated carboxylic reactant per mole of the halogenated backbones. Alternatively, the backbone and the monounsaturated carboxylic reactant are mixed and heated while adding chlorine to the hot material.

WO 2010/115595 10 PCT/EP2010/002132 While chlorination normally helps increase the reactivity of starting olefin polymers with monounsaturated functionalizing reactant, it is not necessary with some of the polymers or hydrocarbons contemplated for use in the present invention, particularly those preferred polymers or hydrocarbons which possess a high terminal bond content and reactivity. Preferably, therefore, the backbone and the monounsaturated functionality reactant, e.g., carboxylic reactant, are contacted at elevated temperature to cause an initial thermal "ene" reaction to take place. Ene reactions are known. The hydrocarbon or polymer backbone can be functionalized by random attachment of functional moieties along the polymer chains by a variety of methods. For example, the polymer, in solution or in solid form, may be grafted with the monounsaturated carboxylic reactant, as described above, in the presence of a free-radical initiator. When performed in solution, the grafting takes place at an elevated temperature in the range of about 100 to 260 0 C, preferably 120 to 240'C. Preferably, free-radical initiated grafting would be accomplished in a mineral lubricating oil solution containing, e.g., I to 50 mass %, preferably 5 to 30 mass % polymer based on the initial total oil solution. The free-radical initiators that may be used are peroxides, hydroperoxides, and azo compounds, preferably those that have a boiling point greater than about 100'C and decompose thermally within the grafting temperature range to provide free-radicals. Representative of these free-radical initiators are azobutyronitrile, 2,5-dimethylhex-3-ene-2, 5-bis-tertiary-butyl peroxide and dicumene peroxide. The initiator, when used, typically is used in an amount of between 0.005% and 1% by weight based on the weight of the reaction mixture solution. Typically, the aforesaid monounsaturated carboxylic reactant material and free-radical initiator are used in a weight ratio range of from about 1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is preferably carried out in an inert atmosphere, such as under nitrogen blanketing. The resulting grafted polymer is characterized by having carboxylic acid (or derivative) moieties randomly attached along the polymer chains: it being understood, of course, that some of the polymer chains remain ungrafted. The free radical grafting described above can be used for the other polymers and hydrocarbons of the present invention. The preferred monounsaturated reactants that are used to functionalize the backbone comprise mono- and dicarboxylic acid material, i.e., acid, or acid derivative material, WO 2010/115595 1 / PCTIEP2010/002132 including (i) monounsaturated C 4 to CIO dicarboxylic acid wherein (a) the carboxyl groups are vicinyl, (i.e., located on adjacent carbon atoms) and (b) at least one, preferably both, of said adjacent carbon atoms are part of said mono unsaturation; (ii) derivatives of (i) such as anhydrides or C, to C 5 alcohol derived mono- or diesters of (i); (iii) monounsaturated C 3 to CIO monocarboxylic acid wherein the carbon-carbon double bond is conjugated with the carboxy group, i.e., of the structure -C=C-CO-; and (iv) derivatives of (iii) such as Ci to C 5 alcohol derived mono- or diesters of (iii). Mixtures of monounsaturated carboxylic materials (i) - (iv) also may be used. Upon reaction with the backbone, the monounsaturation of the monounsaturated carboxylic reactant becomes saturated. Thus, for example, maleic anhydride becomes backbone-substituted succinic anhydride, and acrylic acid becomes backbone-substituted propionic acid. Exemplary of such monounsaturated carboxylic reactants are fumaric acid, itaconic acid, maleic acid, maleic anhydride, chloromaleic acid, chloromaleic anhydride, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl (e.g., C, to C 4 alkyl) acid esters of the foregoing, e.g., methyl maleate, ethyl fumarate, and methyl fumarate. To provide the required functionality, the monounsaturated carboxylic reactant, preferably maleic anhydride, typically will be used in an amount ranging from about equimolar amount to about 100 mass % excess, preferably 5 to 50 mass % excess, based on the moles of polymer or hydrocarbon. Unreacted excess monounsaturated carboxylic reactant can be removed from the final dispersant product by, for example, stripping, usually under vacuum, if required. The treat rate of additives (A) and (B) contained in the lubricating oil composition may for example be in the range of I to 2.5, preferably 2 to 20, more preferably 5 to 18, mass CO-ADDITIVES The lubricating oil composition of the invention may comprise further additives, different from and additional to (A) and (B). Such additional additives may, for example include ashless dispersants, other metal detergents, anti-wear agents such as zinc dihydrocarbyl dithiophosphates, anti-oxidants and demulsifiers.

WO 2010/115595 1 5 PCT/EP2010/002132 It may be desirable, although not essential, to prepare one or more additive packages or concentrates comprising the additives, whereby additives (A) and (B) can be added simultaneously to the base oil to form the lubricating oil composition. Dissolution of the additive package(s) into the lubricating oil may be facilitated by solvents and by mixing accompanied with mild heating, but this is not essential. The additive package(s) will typically be formulated to contain the additive(s) in proper amounts to provide the desired concentration, and/or to carry out the intended function in the final formulation when the additive package(s) is/are combined with a predetermined amount of base lubricant. Thus, additives (A) and (B), in accordance with the present invention, may be admixed with small amounts of base oil or other compatible solvents together with other desirable additives to form additive packages containing active ingredients in an amount, based on the additive package, of, for example, from 2.5 to 90, preferably from 5 to 75, most preferably from 8 to 60, mass % of additives in the appropriate proportions, the remainder being base oil. The final formulations as a trunk piston engine oil may typically contain 30, preferably 10 to 28, more preferably 12 to 24, mass % of the additive package(s), the remainder being base oil. Preferably, the trunk piston engine oil has a compositional TBN (using ASTM D2896) of 20 to 60, such as 25 to 55. EXAMPLES The present invention is illustrated by but in no way limited to the following examples. COMPONENTS The following components were used: Component (A): (Al) a calcium salicylate detergent having a TBN of 350 (basicity index of two or greater; a degree of carbonation of 80% or greater) WO 2010/115595 1 PCT/EP2010/002132 (A2) a calcium salicylate detergent having a TBN of 225 (basicity index of two or greater; a degree of carbonation of less than 80%) (A3) a calcium salicylate detergent having a TBN of 65 (basicity index of less than two; a degree of carbonation of less than 80%) Component (B): (BI) oleic acid (B2) polyisobutene succinic acid derived from a polyisobutene having a number average weight of 450 (B3) a polyisobutene succinic anhydride ("PIBSA") derived from a polyisobutene of number average molecular weight 950 (72% ai) (B4) polyisobutene succinic anhydride ("PIBSA") derived from polyisobutene having a number average molecular weight of 450 (75% ai) (B5) iso-octadecyl succinic anhydride (B6) bis (2-hydroxypropyl) 2-dodecyl succinate (B7) oleamide (B8) tetraethylenepentamine, di-iso-octadecyl amide. Base oil I: an API Group I base oil known as XOMAPE600 Base oil II: an API Group II base oil known as CHEV600R HFO: a heavy fuel oil, ISO-F-RMK 380 WO 2010/115595 LU PCT/EP2010/002132 Phenate: a calcium phenate detergent having a TBN of 255 Sulfonate: a calcium sulfonate detergent having a TBN of 425 LUBRICANTS Selections of the above components were blended to give a range of trunk piston marine engine lubricants. Some of the lubricants are examples of the invention; others are reference examples for comparison purposes. The compositions of the lubricants tested when each contained HFO are shown in the tables below under the "Results" heading. TESTING Panel Coker Test The Panel Coker test was used to evaluate the performance of test lubricants. The test method involved splashing the oil under test onto a heated metal plate by spinning a metal comb-like device within a sump containing the oil. At the end of the test period, deposits formed may be assessed by weight and by visual inspection of the plate's appearance. The testing was performed using a panel coker tester, model PK-S, supplied by the Yoshida Kagaku Kikai Co., of Osaka, Japan. Test panels were thoroughly cleaned and then weighed before inserting them into the apparatus. The test oil was mixed with 2.5% HFO and 225g of the resulting mixture added to the sump of the apparatus. When the temperature of the oil was at 100'C and the test plate at 320'C, a metal comb device was automatically rotated causing the oil to be splashed onto the test plate. The test sequence lasted for 120 cycles, each cycle consisting of 15 seconds in which the oil was splashed onto the plate and 45 seconds without splashing. At the end of test, the plate was washed with n-heptane, dried, reweighed and visually examined. The deposit weight was reported.

WO 2010/115595 21 PCTIEP2010/002132 Light Scattering Test lubricants were also evaluated for asphaltene dispersancy using light scattering according to the Focused Beam Reflectance Method ("FBRM"), which predicts asphaltene agglomeration and hence 'black sludge' formation. The FBRM test method was disclosed at the 7th International Symposium on Marine Engineering, Tokyo, 2 4 1h - 2 8 th October 2005, and was published in 'The Benefits of Salicylate Detergents in TPEO Applications with a Variety of Base Stocks', in the Conference Proceedings. Further details were disclosed at the C1MAC Congress, Vienna, 2 1 t - 2 4 h May 2007 and published in "Meeting the Challenge of New Base Fluids for the Lubrication of Medium Speed Marine Engines - An Additive Approach" in the Congress Proceedings. In the latter paper it is disclosed that by using the FBRM method it is possible to obtain quantitative results for asphaltene dispersancy that predict performance for lubricant systems based on basestocks containing greater than or less than 90% saturates, and greater than or less than 0.03% sulphur. The predictions of relative performance obtained from FBRM were confirmed by engine tests in marine diesel engines. The FBRM probe contains fibre optic cables through which laser light travels to reach the probe tip. At the tip, an optic focuses the laser light to a small spot. The optic is rotated so that the focussed beam scans a circular path between the window of the probe and the sample. As particles flow past the window they intersect the scanning path, giving backscattered light from the individual particles. The scanning laser beam travels much faster than the particles; this means that the particles are effectively stationary. As the focussed beam reaches one edge of the particle there is an increase in the amount of backscattered light; the amount will decrease when the focussed beam reaches the other edge of the particle. The instrument measures the time of the increased backscatter. The time period of backscatter from one particle is multiplied by the scan speed and the result is a distance or chord length. A chord length is a straight line between any two points on the edge of a particle. This is represented as a chord length distribution, a graph of numbers of chord lengths (particles) measured as a function of the chord length dimensions in microns. As the measurements are performed in real time the statistics of a distribution can be calculated and WO 2010/115595 22 PCT/EP2010/002132 tracked. FBRM typically measures tens of thousands of chords per second, resulting in a robust number-by-chord length distribution. The method gives an absolute measure of the particle size distribution of the asphaltene particles. The Focused beam Reflectance Probe (FBRM), model Lasentec D600L, was supplied by Mettler Toledo, Leicester, UK. The instrument was used in a configuration to give a particle size resolution of 1 jtm to 1mm. Data from FBRM can be presented in several ways. Studies have suggested that the average counts per second can be used as a quantitative determination of asphaltene dispersancy. This value is a function of both the average size and level of agglomerate. In this application, the average count rate (over the entire size range) was monitored using a measurement time of I second per sample. The test lubricant formulations were heated to 60'C and stirred at 400rpm; when the temperature reached 60'C the FBRM probe was inserted into the sample and measurements made for 15 minutes. An aliquot of heavy fuel oil (10% w/w) was introduced into the lubricant formulation under stirring using a four blade stirrer (at 400 rpm). A value for the average counts per second was taken when the count rate had reached an equilibrium value (typically overnight). RESULTS Panel Coker Test The results of the Panel Coker tests are summarized in the tables below where figures are mass % of active ingredient unless otherwise stated. TABLE 1 Ex I Ca salicylate (Al) [ PIBSA (B3) | Base oil I I Base oil II Deposits (g) 1 8.57 7.00 - 84.43 0.0221 X 8.57 - 91.43 0.0759 Y 8.57 - 91.43 0.0450 Each lubricant contained 44.6 mM of soap and had a TBN of 30. Also, each lubricant contained 0.5 mass % HFO.

WO 2010/115595 2J PCT/EP2010/002132 The results show that the example of the invention (Ex 1) gave rise to much lower deposits, i.e. improved asphaltene dispersency, than a corresponding example lacking PIBSA (Ex X) and also than an example in a Group I base oil lacking PIBSA (Ex Y). TABLE2 Ex Ca phenate Ca sulfonate PIBSA (B3) Base oil II Deposits (g) P 4.40 4.40 7.00 84.20 0.1489 Q 4.40 4.40 - 91.20 0.1009 Each lubricant contained 42 mM of soap and had a TBN of 30. Also, each lubricant contained 0.5 mass % HFO. The results show that the presence of PIBSA (Ex P) diminishes the asphaltene handling performance when the detergent is a phenate/sulfonate combination. This contrasts with the finding of TABLE 1 that, when the detergent is a salicylate, the performance is improved.

WO 2010/115595 /- PCT/EP2010/002132 Light Scattering Results of the FBRM tests are summarised in TABLE 3 below. TABLE 3 Ex Ca salicylate (Al) Component (B) Particle count/s (mass % a.i.) (2.6 mass % a.i.) Ref 2.6 1,128 B1 4,777 2.6 B1 175 - B2 3,944 2.6 B2 486 - B3 3,763 2.6 B3 168 - B4 5,640 2.6 B4 167 B5 5,073 2.6 B5 240 - B6 6,559 2.6 B6 363 - B7 16,523 2.6 B7 859 B8 2,110 2.6 B8 294 The results show that, in all cases, (A) plus (B) is better than (A) alone.

WO 2010/115595 PCT/EP2010/002132 Further results of FBRM, carried out separately from those of TABLE 3 in a recalibrated instrument, are summarised in TABLE 4 below. TABLE 4 Ex Ca Salicylate (A) Component (B3) Particle count/s (mass % a.i.) (mass % a.i.) Ref - 2.6 13,710 Al (2.6) - 15,888 A 1 (2.6) 2.6 4,355 Ref - 2.1 15,191 A2 (2.1) 8,782 A2 (2.1) 2.1 6,149 A2 (2.1) 2.6 3,438 Ref - 1.8 15,564 A3 (1.8) - 10,748 A3 (1.8) 1.8 5,803 A3 (1.8) 2.6 3,629 The results show that (A), represented by each of A1, A2 and A3, in combination with (B3) is better than (A) alone and better than (B3) alone.

Claims

1. A trunk piston marine engine lubricating oil composition for improving asphaltene handling in use thereof, in operation of the engine when fuelled by a heavy fuel oil, which composition includes or is made by admixing an oil of 5 lubricating viscosity, in a major amount, containing 50 mass % or more of a Group 11 basestock, and, in respective minor amounts: (A) an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent other than such a detergent having a basicity index of less than two 10 and a degree of carbonation of 80% or greater, where degree of carbonation is the percentage of carbonate present in the overbased metal hydrocarbyl substituted hydroxybenzoate detergent expressed as a mole percentage relative to the total excess base in the detergent; and 15 (B) a hydrocarbyl-substituted carboxylic acid or anhydride thereof, wherein the or at least one hydrocarbyl group contains at least eight carbon atoms, the acid or anhydride constituting at least 1 and up to 10 mass % of the lubricating oil composition.

2. The compositon as claimed in claim 1, wherein in (B) said at least one 20 hydrocarbyl group contains at least eight atoms, the acid or anhydride constituting 1.5 to 10 mass % of the lubricating oil composition.

3. The composition as claimed in claim 1 or 2 wherein (A) has (Al) a basicity index of two or greater and a degree of carbonation of 80% or greater; or 25 (A2) a basicity index of two or greater and a degree of carbonation of less than 80%; or (A3) a basicity index of less than two and a degree of carbonation of less than 80%.

4. The composition as claimed in claim 1, 2 or 3 wherein (B) is depicted as: 27 R' HC-COX H 2 C-COY (I) where R' represents a C8 to C 100 branched or linear hydrocarbyl; X and Y each independently represents OR 2 and OR 3 , where each R 2 and 5 R 3 independently represents a hydrogen atom or an alkyl, aryl or aralkyl group, or X and Y together represent -0-; and/or depicted as R 1 CH 2 COR 4 (II) 10 where R 1 is defined as above; R 4 represents OR 5 or NR 6 R , where each R 5 , R 6 and R 7 independently represents a hydrogen atom or an alkyl group.

5. The composition as claimed in claim 4, wherein R 1 is a branched or linear hydrocarbyl selected from the group consisting of a polyalkenyl, alkyl or alkaryl 15 group.

6. The composition as claimed in any one of claims 1 to 5 wherein the metal in (A) is calcium.

7. The composition as claimed in any one of claims 1 to 6 wherein the hydrocarbyl- substituted hydroxybenzoate in (A) is a salicylate. 20

8. The composition as claimed in any one of claims 1 to 7 wherein the oil of lubricating viscosity contains more than 60 mass % of a Group 11 basestock.

9. The composition as claimed in any one of claims 1 to 8 wherein the hydrocarbyl group in (B) has from 8 to 400 carbon atoms. 28

10. The composition as claimed in any one of claims 1 to 8 wherein the hydrocarbyl group in (B) has from 12 to 100 carbon atoms.

11. The composition as claimed in any one of claims 1 to 8 wherein the hydrocarbyl group in (B) has from 16 to 64 carbon atoms. 5

12. The composition as claimed in any one of claims 1 to 11 wherein, in the acid or derivative (B), the hydrocarbyl substituent is derived from a polyolefiin.

13. The composition as claimed in any one of claims 1 to 12 wherein (B) is a succinic acid or a succinic anhydride.

14. The composition as claimed in claim 13 wherein (B) is a polyisobutene 10 succinic acid or anhydride.

15. The composition as claimed in any one of claims 1 to 14 having a TBN of 20 to 60.

16. The composition as claimed in any one of claims 1 to 14 having a TBN of 25 to 55. 15

17. The use of a detergent (A) as defined in any one of claims 1 to 16 in combination with a carboxylic acid or anhydride as defined in, and in the amount stated in any one of the preceding claims, in a trunk piston marine lubricating oil composition for a medium-speed compression-ignited marine engine, which composition includes an oil of lubricating viscosity in a major amount and contains 20 50 mass % or more of a Group II basestock containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur or a mixture thereof, to improve asphaltene handling during operation of the engine, fueled by a heavy fuel oil, and its lubrication by the composition, in comparison with analogous operation when the same amount of detergent (A) is used in the absence of (B). 25 29

18. A method of operating a trunk piston medium-speed compression-ignited marine engine including (i) fueling the engine with a heavy fuel oil; and (ii) lubricating the crankcase of the engine with a composition as defined in 5 any one of claims 1 to 16.

19. A method of dispersing asphaltenes in a trunk piston marine lubricating oil composition during its lubrication of surfaces of the combustion chamber of a medium-speed compression-ignited marine engine and operation of the engine, which method includes 10 (i) providing a composition as defined in any one of claims 1 to 16; (ii) providing the composition in the combustion chamber; (iii) providing heavy fuel oil in the combustion chamber; and (iv) combusting the heavy fuel oil in the combustion chamber.

20. A trunk piston marine engine lubricating oil composition for improving 15 asphaltene handling in use thereof, in the engine when fuelled by a heavy fuel oil, substantially as described herein. INFINEUM UK LIMITED WATERMARK PATENT & TRADE MARK ATTORNEYS P35028AU00