Marine lubricating oil composition

Abstract

A marine engine lubricating oil composition comprising: (a) at least 40% by weight of an oil of lubricating viscosity having a kinematic viscosity at 100 DEG C of from 4.0 to less than 8.0 mm2 / s; and (b) one or more polyisobutylene thickeners having a number average molecular weight of from 400 to 6,000 Daltons. The marine lubricating oil composition has a TBN of less than 70 mg KOH / g. The marine lubricating oil composition is a single-stage lubricating oil composition which meets the requirements of the SAE J300 standard revised in January 2015 on SA E 20, SAE 30, SAE 40, SAE 50 or SAE 60 single-stage lubricating oil.

Description

Technical Field

[0001] The present disclosure relates to lubricating oil compositions, and more particularly, to the use of light neutral base oils and polyisobutene thickeners in marine lubricating oil compositions. Background Art

[0002] This section is intended to introduce to the reader various aspects of the technology that may be related to the various aspects of the present disclosure described and / or claimed below. It is believed that this discussion will help to provide the reader with background information to better understand the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light and not as an admission of prior art.

[0003] Marine internal combustion engines are generally classified as low-speed, medium-speed or high-speed engines. Low-speed engines are unique in terms of size and operating method. These engines are quite large and typically operate in the range of about 60 to 200 revolutions per minute (rpm). Low-speed engines operate on a two-stroke cycle and are typically direct-connected and direct-reversing engines of the "crosshead" configuration, where diaphragms and one or more stuffing boxes separate the power cylinders from the crankcase to prevent combustion products from entering the crankcase and mixing with the crankcase oil. Marine two-stroke cylinder lubricants must meet performance requirements to accommodate the severe operating conditions required for more modern large-bore engines operating at significantly varying outputs, loads and cylinder liner temperatures. Since the crankcase is completely separated from the combustion zone, those skilled in the art use different lubricating oils to lubricate the combustion chamber and the crankcase, which are referred to as cylinder lubricants and system oils, respectively. Marine cylinder lubricants and system oils are subject to their own unique requirements.

[0004] In a two-stroke crosshead engine, the cylinders are lubricated on a total-loss basis, and the cylinder oil is sprayed onto each cylinder separately by lubricators positioned around the cylinder liner. The cylinder lubricant is not recycled and is burned with the fuel. The cylinder lubricant is required to provide a robust film between the cylinder liner and the piston rings for adequate lubrication of the cylinder wall to prevent scuffing, and also needs to have thermal stability so that the lubricant does not form deposits on the hot surfaces of the piston and piston rings, and is capable of neutralizing sulfur-based acidic combustion products. In contrast to the cylinder lubricant, the system oil is not exposed to the combustion chamber in which the fuel burns and is formulated to last as long as possible to maximize the life of the oil.

[0005] The crankshaft and crosshead of a system-oil lubricated two-stroke engine. It lubricates the main bearings, crosshead bearings, gears and camshafts, cools the underside structure of the piston crown and protects the crankcase from corrosion. The system oil needs to be able to prevent metal corrosion in the bearing shells and prevent rusting of the crankcase in the presence of contaminated water. The system oil also needs to provide sufficient hydrodynamic lubrication for the bearings and have an anti-wear system sufficient to provide wear protection for the bearings and gears under extreme pressure conditions. In contrast to cylinder lubricants, the system oil is not exposed to the combustion chamber in which the fuel burns and is formulated to last as long as possible to maximize the life of the oil. Therefore, the main performance characteristics of the system oil are related to wear protection, oxidation stability, viscosity increase control and deposit performance.

[0006] Unlike two-stroke crosshead engines, medium-speed engines typically operate in the range of about 250 to 1100 rpm and operate on a four-stroke cycle. These engines typically have a trunk piston design. In a trunk piston engine, in contrast to a crosshead engine, a single lubricating oil is used to lubricate all areas of the engine. Therefore, trunk piston engine oils have unique requirements when compared to marine cylinder lubricants. The key lubricant performance parameters for operating a trunk piston engine include deposit control in the piston cooling oil cavity and piston ring pack, oxidation and viscosity increase control, demulsibility performance and sludge control. For marine residual fuel operation, these performance parameters are almost entirely driven by asphaltene contamination from marine residual fuel.

[0007] Recently, due to health and environmental considerations, relevant regulations have stipulated that marine engines must use fuels with lower sulfur content. Therefore, manufacturers are now designing marine engines to be used with a variety of fuels, such as carbon-based gaseous fuels (e.g., natural gas, biogas, landfill gas, wood gas, methane, propane, butane, ethylene, etc.), non-carbon-based gaseous fuels (e.g., ammonia, hydrogen), liquid ammonia, liquefied petroleum gas (LPG), alcohol-based fuels (e.g., methanol, ethanol), dimethyl ether and high-quality distillate fuels, as well as poorer quality medium or heavy fuels, such as marine residual fuels with generally higher sulfur and higher asphaltene content. For operation without residual fuel, the fuel does not contain significant asphaltenes present in the fuel and contains a much lower sulfur level. When lower sulfur fuels burn, less acid is formed in the combustion chamber.

[0008] One of the main features in which a lubricant helps protect a marine engine is the "thickness", i.e., viscosity, of the lubricating oil film. Lubricants used to lubricate marine internal combustion engines have high viscosity industrial requirements due to low operating speeds and high loads, and are typically high viscosity single grade lubricants of SAE 20, SAE 30, SAE 40, SAE 50 or SAE 60 viscosity grades (i.e., lubricants that exhibit little or no viscosity index improver characteristics). Since hydrocracking causes a loss of viscosity in the base oil, marine oils cannot generally be formulated solely with hydrocracked base oils. To obtain a suitable lubricating oil film thickness, conventional marine formulations typically include a large amount of heavy neutral base oil and / or high viscosity bright stock in the marine lubricant. Bright stock is a highly refined and dewaxed high viscosity base oil produced from residual oil or bottoms oil.

[0009] However, the reliance on bright stock is not always desirable due to the presence of oxidation-unstable aromatic compounds. In addition, the supply of bright stock is also continuously decreasing, leading to the need for alternative solutions to impart the required viscosity to the lubricating oil when a large amount of bright stock (such as those used in marine engines) is used. Considering the increasing severity of making changes as modern marine engine designs change, requirements related to fuel quality change, and the decline in bright stock availability, there has been a continuing need for improved marine lubricant formulation techniques that provide improved performance while achieving the high viscosity required for marine cylinder lubricants. SUMMARY OF THE INVENTION

[0010] An overview of certain embodiments disclosed herein is described below. It should be understood that these aspects are presented only to provide a brief overview of these particular embodiments to the reader and are not intended to limit the scope of the present disclosure. Indeed, the present disclosure may cover a number of aspects that may not be set forth below.

[0011] Generally, in one aspect, the present disclosure relates to a marine engine lubricating oil composition comprising (a) at least 40 wt% of an oil having lubricating viscosity, the oil having a kinematic viscosity of 4.0 to less than 8.0 mm 2 / s at 100 °C; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 daltons. The marine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a single grade lubricating oil composition that meets the requirements of the SAE J300 specification revised in January 2015 for SAE 20, SAE 30, SAE 40, SAE 50 or SAE 60 single grade lubricating oils.

[0012] In another aspect, the present disclosure relates to a method of thickening a lubricating oil composition in a marine internal combustion engine. The method includes adding to the engine a lubricating oil composition comprising: (a) at least 40 wt% of an oil having lubricating viscosity, the oil having a kinematic viscosity of 4.0 to less than 8.0 mm 2 / s at 100 °C; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 Daltons. The marine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a single grade lubricating oil composition that meets the requirements of the SAE J300 specification, revised in January 2015, for SAE 20, SAE 30, SAE 40, SAE 50, or SAE 60 single grade lubricating oils.

[0013] In another aspect, the present disclosure relates to a method of controlling deposit formation in an internal combustion engine. The method includes operating the internal combustion engine with a lubricating oil composition. The lubricating oil composition comprises: (a) at least 40 wt% of an oil having lubricating viscosity, the oil having a kinematic viscosity of 4.0 to less than 8.0 mm 2 / s at 100 °C; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 Daltons. The marine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a single grade lubricating oil composition that meets the requirements of the SAE J300 specification, revised in January 2015, for SAE 20, SAE 30, SAE 40, SAE 50, or SAE 60 single grade lubricating oils. DETAILED DESCRIPTION

[0014] Definition

[0015] In this specification, the following words and expressions, if used and when used, have the meanings given below.

[0016] "Major amount" means greater than 40 wt% of the composition.

[0017] "Minor amount" means less than 40 wt% of the composition.

[0018] "Marine residual fuel" means a material combustible in large marine engines, having at least 2.5 wt% (e.g., at least 5 wt%, or at least 8 wt%) (relative to the total weight of the fuel) of carbon residues (as defined in ISO 10370), a viscosity greater than 14.0 cSt at 50 °C, such as marine residual fuel as defined in ISO 8217:2005, "Petroleum products--Fuels (class F)--Specifications of marine fuels", the content of which is incorporated herein by reference in its entirety.

[0019] "Residual fuel" means a fuel meeting the specifications of residual marine fuel as described in ISO 8217:2010 International Standard. "Low sulfur residual fuel" means a fuel meeting the specifications of residual marine fuel as described in ISO 8217:2010 Specification, having additionally about 1.5 wt% or less, or even about 0.5 wt% or less sulfur relative to the total weight of the fuel.

[0020] "Distillate fuel" means a fuel meeting the specifications of distillate marine fuel as described in ISO 8217:2010 International Standard. "Low sulfur distillate fuel" means a fuel meeting the specifications of distillate marine fuel as described in ISO 8217:2010 International Standard, having additionally about 0.1 wt% or less, or even about 0.005 wt% or less sulfur relative to the total weight of the fuel.

[0021] "Low sulfur fuel" means a fuel having about 1.5 wt% or less, or even about 1.0 wt% or less, or even 0.5 wt% or less, or even 0.1 wt% or less sulfur relative to the total weight of the fuel.

[0022] "High sulfur fuel" is a fuel having greater than 1.5 wt% sulfur relative to the total weight of the fuel.

[0023] The term "on an active basis" means an additive material that is not diluent oil or solvent.

[0024] As used in this specification and the claims, "α-olefin" refers to an olefin having a carbon-carbon double bond between the first and second carbon atoms of the longest continuous chain of carbon atoms. The term "α-olefin" includes straight-chain and branched α-olefins, unless otherwise expressly stated. In the case of a branched α-olefin, the branch can be at the 2-position (vinylidene) and / or at the 3-position or higher relative to the olefin double bond. Whenever used in this specification and the claims, the term "vinylidene" refers to an α-olefin having a branch at the 2-position relative to the olefin double bond. α-Olefins are almost always mixtures of isomers and are usually also mixtures of compounds having a certain range of carbon numbers. Low molecular weight α-olefins, such as C6, C8, C 10 , C 12 and C 14 α-olefins are almost exclusively 1-olefins. Higher molecular weight olefin fractions such as C 16 -C 18 or C 20 -C 24 have an increasing proportion of double bonds isomerized to internal or vinylidene positions

[0025] "Normal α-olefin" (NAO) refers to a straight-chain aliphatic monoolefin having a carbon-carbon double bond between the first and second carbon atoms. It should be noted that "normal α-olefin" is not synonymous with "straight-chain α-olefin" since the term "straight-chain α-olefin" can include straight-chain olefinic compounds having a double bond between the first and second carbon atoms.

[0026] "Isomerized olefin" or "isomerized normal α-olefin" refers to an olefin obtained by isomerizing an olefin. Generally, the isomerized olefin has a double bond at a position different from that of the starting olefin from which it is derived and can also have different properties.

[0027] "Isomerization level (I)" refers to the isomerization level measured by an NMR method. The isomerization level of an olefin is determined by hydrogen-1 (1H) NMR. The NMR spectrum is obtained on a Bruker Ultrashield Plus 400 in chloroform-d at 400 MHz using TopSpin 3.2 spectral processing software. The isomerization level represents the relative amount of methyl groups (—CH3) (chemical shift 0.30 to 1.01 ppm) attached to the methylene backbone group (—CH2—) (chemical shift 1.01 to 1.38 ppm) and is defined by the equation (I) = m / (m + n), where m is the NMR integral of the methyl groups having a chemical shift between 0.30 ± 0.03 and 1.01 ± 0.03 ppm and n is the NMR integral of the methylene groups having a chemical shift between 1.01 ± 0.03 and 1.38 ± 0.10 ppm.

[0028] The term "total base number" or "TBN" or "BN" refers to the alkalinity level in an oil sample according to ASTM standard number D2896 or an equivalent procedure, which represents the ability of the composition to continue to neutralize corrosive acids. This test measures the change in conductivity, and the result is expressed as mg KOH / g (the milliequivalent number of KOH required to neutralize 1 gram of the product). Thus, a high TBN reflects a strongly overbased product and therefore a higher reserve of base for neutralizing acids. When TBN values are introduced herein, it should be understood that they are expressed in units of mgKOH / g.

[0029] "Overbased" is used to describe a metal detergent in which the ratio of the equivalent number of the metal portion to the equivalent number of the acid portion is greater than one.

[0030] "Soap" means a neutral detergent compound that contains approximately stoichiometric amounts of metal to effect the neutralization of one or more acidic groups present in the organic acid used to prepare the detergent.

[0031] "Metal" means an alkali metal, an alkaline earth metal, or a mixture thereof. When an alkali metal is employed, the alkali metal is lithium, sodium, or potassium. When an alkaline earth metal is employed, the alkaline earth metal can be selected from the group consisting of calcium, barium, magnesium, and strontium. Calcium and magnesium are preferred.

[0032] Unless otherwise expressly stated, "weight percent" (wt%) refers to the percentage of the listed component, compound, or substituent based on the total weight of the entire composition. Unless otherwise indicated, all reported percentages are based on the weight percent of the active ingredient (i.e., without considering the carrier or diluent oil). The diluent oil used for lubricant additives can be any suitable base oil (e.g., Group I base oil, Group II base oil, Group III base oil, Group IV base oil, Group V base oil, or a mixture thereof). The weight percent representing the combination of the ingredient and the carrier or diluent oil is referred to as the "as is" weight percent.

[0033] The term "sulfated ash content" refers to the amount of metal-containing additives (e.g., calcium, magnesium, molybdenum, zinc) in a lubricating oil composition and is typically measured according to ASTM D874, which is incorporated herein by reference.

[0034] Lubricating oil composition

[0035] It has surprisingly been found that replacing (e.g., fully or partially) heavy neutral base stocks and bright stocks with a combination of lighter neutral base stocks and polyisobutene thickeners in marine lubricants provides a marine lubricating oil composition that exhibits improved resistance to deposit formation and oxidative stability in engines operating under various load conditions (such as high load conditions), while achieving a suitable lubricating oil viscosity.

[0036] In certain embodiments, the lubricating oil compositions of the present disclosure are marine engine lubricating oils. In such embodiments, the lubricating oil composition comprises (a) at least 40 wt% of an oil having lubricating viscosity, the oil having a kinematic viscosity of 4.0 to less than 8.0 mm 2 / s at 100 °C; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 daltons; wherein the lubricating oil composition is a single-grade lubricating oil composition that meets the requirements of the SAE J300 specification, revised in January 2015, for SAE 20, 30, 40, 50, or 60 single-grade engine oils and has a TBN of less than 70 mg KOH / g, as determined by ASTM D2896. The kinematic viscosity of the oil having lubricating viscosity may correspond to the viscosity of a light neutral base stock.

[0037] The lubricating oil composition may be a single-grade lubricating oil composition that meets the requirements of the SAE J300 specification, revised in January 2015, for 20, 30, 40, 50, or 60 single-grade engine oils. The SAE 20 oil has a kinematic viscosity of 6.9 to <9.3 mm 2 / s at 100 °C. The SAE 30 oil has a kinematic viscosity of 9.3 to <12.5 mm 2 / s at 100 °C. The SAE 40 oil has a kinematic viscosity of 12.5 to <16.3 mm 2 / s at 100 °C. The SAE 50 oil has a kinematic viscosity of 16.3 to <21.9 mm 2 / s at 100 °C. The SAE 60 oil has a kinematic viscosity of 21.9 to <26.1 mm 2 / s at 100 °C.

[0038] In some embodiments, the lubricating oil composition is suitable for use as a marine cylinder lubricant (MCL). The marine cylinder lubricants of the present disclosure are manufactured to SAE 40, SAE 50, or SAE 60 single-grade specifications to provide a sufficiently thick lubricant film on the cylinder liner walls at high temperatures.

[0039] In addition to providing a sufficient degree of lubricity, one of the main functions of a marine cylinder lubricant is to neutralize the sulfur-based acidic components of the combusted sulfur-containing fuel. This neutralization is typically achieved by including basic substances such as overbased metal detergents. The neutralization ability of the oil is characterized by its alkalinity and is measured by its total base number (TBN). Generally, sulfur-containing fuels used to operate marine engines require marine cylinder lubricants to have high detergency and neutralization ability, even if the oil is only exposed to heat and other stresses for a short period of time. On the other hand, low-sulfur fuels may not require as high a neutralization ability as sulfur-containing fuels.

[0040] To allow for sufficient neutralization and detergency while maintaining a relatively low level of deposits, the marine cylinder lubricants of the present disclosure have a TBN of less than 70 mg KOH / g. By way of example, the TBN can be in the range of less than 70 to 2 mg KOH / g, or less than 70 to 5 mg KOH / g, or less than 70 to 10 mg KOH / g, less than 70 to 15 mg KOH / g, less than 70 to 20 mg KOH / g, 60 to 2 mg KOH / g, 60 to 5 mg KOH / g, 60 to 10 mg KOH / g, 60 to 15 mg KOH / g, 60 to 20 mg KOH / g, 50 to 2 mgKOH / g, 50 to 5 mg KOH / g, 50 to 10 mg KOH / g, 50 to 15 mg KOH / g or 50 to 20 mg KOH / g. Further by way of example, the TBN can be in the range of less than 40 to 2 mg KOH / g, or less than 40 to 5 mg KOH / g, or less than 40 to 10 mg KOH / g, less than 40 to 15 mg KOH / g, or less than 40 to 20 mg KOH / g. In certain embodiments, the TBN is in the range of 40 to 15 mg KOH / g.

[0041] In some embodiments, the lubricating oil compositions of the present invention are suitable for use as marine trunk piston engine oils (TPEO). The marine TPEO lubricants of the present disclosure are prepared according to SAE 30 or SAE 40 single grade specifications. Such marine TPEO lubricants have a TBN in the range of greater than 15 to 70 mg KOH / g (e.g., 30 to 70 mg KOH / g, 35 to 65 mg KOH / g, 40 to 60 mg KOH / g).

[0042] In other embodiments, the lubricating oil compositions of the present invention are suitable for use as system oils (SO). The marine SO lubricants of the present disclosure are prepared according to SAE 20 and SAE 30 single grade specifications. Such marine SO lubricants have a TBN in the range of 2 to 20 mg KOH / g (e.g., 5 to 20, 5 to 15, 5 to 12, 7 to 20, 7 to 15, 7 to 12, 8 to 20, 8 to 15 or 8 to 12 mg KOH / g).

[0043] In certain embodiments, the lubricating oil compositions of the present disclosure have a sulfated ash content of at least 1.50 wt% as determined by ASTM D874. For example, the lubricating oil compositions of the present disclosure can have a sulfated ash level of 1.5 to 27 wt% as determined by ASTM D 874. Further by way of example, the lubricating oil compositions of the present disclosure can have a sulfated ash content of 2.0 to 25.0 wt%, 2.5 to 25.0 wt%, 3.0 to 25.0 wt%, or 5.0 to 25.0 wt% as determined by ASTM D 874.

[0044] Oil with lubricating viscosity

[0045] The lubricating oil compositions of the present disclosure have at least 40 wt% of an oil having a lubricating viscosity, based on the total weight of the composition, such as at least 50 wt% (e.g., at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt%). For example, the lubricating oil compositions of the present disclosure can comprise 40 wt% to 95 wt%, 50 wt% to 90 wt%, 55 wt% to 85 wt% of an oil having a lubricating viscosity. An oil having a lubricating viscosity can also be referred to as a base oil.

[0046] According to certain embodiments of the present disclosure, the oil having a lubricating viscosity has a kinematic viscosity at 100 °C of 4.0 mm 2 / s to less than 8.0 mm 2 / s. For example, the oil having a lubricating viscosity can have a kinematic viscosity at 100 °C of 4.0 mm 2 / s to 7.5 mm 2 / s, or 4.5 mm 2 / s to 7.5 mm 2 / s, or 5.0 mm 2 / s to 7.5 mm 2 / s.

[0047] The oil having a lubricating viscosity of the present disclosure can include only one base oil component, or can include a mixture of two or more base oil components to achieve the above kinematic viscosity. The oil having a lubricating viscosity can be selected from any of the Group I-V base oils specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines (API 1509). The five base oil groups are summarized in Table 1:

[0048] Table 1

[0049]

[0050] (1)ASTM D2007

[0051] (2) ASTM D2270

[0052] (3) ASTM D3120, ASTM D4294 or ASTM D4297

[0053] Groups I, II, and III are mineral oil processed oils. Group IV base oils contain true synthetic molecular substances, which are produced by the polymerization of olefinically unsaturated hydrocarbons. Many Group V base oils are also true synthetic products and can include diesters, polyol esters, polyalkylene glycols, alkylated aromatics, polyphosphates, polyethylene ethers, and / or polyphenylene ethers, etc., but can also be naturally occurring oils such as vegetable oils. It should be noted that although Group III base oils are derived from mineral oils, the rigorous processing these fluids undergo makes their physical properties very similar to some true synthetic substances such as PAO. Thus, oils derived from Group III base oils can be referred to as synthetic fluids in the industry.

[0054] The base oils used in the disclosed lubricating oil compositions can be mineral oils, animal oils, vegetable oils, synthetic oils, semi-synthetic oils, bio-based oils, or mixtures thereof. Suitable oils can be derived from hydrocracked, hydrogenated, hydrorefined, unrefined, refined, and re-refined oils, and mixtures thereof.

[0055] Unrefined oils are those oils derived from natural, mineral, or synthetic sources without or with little further purification treatment. Refined oils are similar to unrefined oils, except that they have been processed in one or more purification steps, which can result in the improvement of one or more properties. Examples of suitable purification techniques are solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Oils refined to edible quality may or may not be useful. Edible oils can also be referred to as white oils. In some embodiments, the lubricating oil compositions do not contain edible oils or white oils.

[0056] Re-refined oils are also known as recycled oils or reprocessed oils. These oils are obtained in a manner similar to refined oils using the same or similar methods. Generally, these oils are additionally processed by techniques involving the removal of spent additives and oil decomposition products.

[0057] Mineral oils can include oils such as liquid petroleum and solvent-treated or acid-treated paraffinic, naphthenic, or mixed paraffin-naphthenic mineral lubricating oils. If desired, such oils may be partially or fully hydrogenated. Oils derived from coal or shale can also be useful.

[0058] Useful synthetic lubricating oils can include hydrocarbon oils such as polymerized, oligomerized or copolymerized olefins (e.g., polybutene, polypropylene, propylene / isobutene copolymer); poly(1-hexene), poly(1-octene), trimers or oligomers of 1-decene such as poly(1-decene), such materials are commonly referred to as α-olefins, and mixtures thereof; alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di-(2-ethylhexyl)-benzene); polyphenyls (e.g., biphenyl, terphenyl, alkylated polyphenyl); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers and alkylated diphenyl sulfides and their derivatives, analogs and homologs or mixtures thereof. Poly-α-olefins are typically hydrogenated materials.

[0059] Other synthetic lubricating oils include polyol esters, diesters, liquid esters containing phosphoric acid (e.g., tricresyl phosphate, trioctyl phosphate and diethyl decanephosphonate) or polymerized tetrahydrofuran. Synthetic oils can be produced by the Fischer-Tropsch reaction and can generally be hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil can be prepared by a Fischer-Tropsch gas-liquid synthesis process and other gas-liquid oils.

[0060] The base oils useful in formulating the lubricating oils for the present disclosure are any of a variety of oils corresponding to API Group I, II, III, IV and V oils and mixtures thereof. In one embodiment, the base oil is a Group II base oil or a blend of two or more different base oils. In another embodiment, the base oil is a Group I base oil or a blend of two or more different Group I base oils. Suitable Group I base oils include any light top fractions from vacuum distillation columns, such as any light neutral, medium neutral and heavy neutral base stocks.

[0061] The base oil can also include residual base stocks or bottoms fractions such as bright stocks. Bright stocks are high-viscosity base oils that are conventionally produced from residual stocks or tower bottoms and have been highly refined and dewaxed. Bright stocks can have a kinematic viscosity greater than 180 mm 2 / s at 40 °C (e.g., greater than 250 mm 2 / s, or even in the range of 500 to 1100 mm 2 / s). In certain embodiments, the lubricating oil composition does not contain bright stock.

[0062] Thickener

[0063] According to an embodiment of the present invention, in order to obtain a finished lubricating oil composition having a desired viscosity grade, a thickener can be added to the lubricating oil composition to increase its viscosity. It has surprisingly been found that replacing heavy neutral base oils and bright stocks with a combination of lighter neutral base oils and polyisobutene thickener (PIB) in marine lubricants provides a lubricating oil composition that exhibits improved resistance to deposit formation and oxidation stability in engines operating under high load conditions while achieving a suitable lubricating oil viscosity.

[0064] Based on the total weight of the composition, the PIB thickener can be present in the lubricating oil composition in an amount of 0.1 to 50 wt% (such as 0.5 to 50 wt%, 1 to 50 wt%, 1 to 40 wt%, 2 to 40 wt%, 3 to 40 wt%, 2 to 35 wt% or 4 to 35 wt%, 1 to 35 wt%, 2 to 30 wt%, 3 to 30 wt%, 5 to 30 wt%, 0.5 to 25 wt%, 1 to 25 wt%, 1 to 20 wt%, 2 to 15 wt% or 4 to 15 wt%). The PIB is generally a viscous oil-miscible liquid having a number average molecular weight of 400 to 6000 daltons (for example, 500 to 5000 daltons, 1000 to 5000 daltons, 1200 to 4000 daltons, 1000 to 2500 daltons, 2000 to 2500 daltons).

[0065] The polyisobutene thickener has a kinematic viscosity at 100 °C in the range of 50 to 50,000 mm 2 / sec, such as 630 to 2,500 mm 2 / sec. Further by way of example, the PIB thickener can have a kinematic viscosity at 100 °C in the range of 2,000 - 6,000 mm 2 / sec, or 2,000 - 5,000 mm 2 / sec, or 3,000 - 4,500 mm 2 / sec. Polybutene, especially polyisobutene or poly-n-butene, can be prepared, for example, by polymerization of C4 refinery streams.

[0066] Other performance additives

[0067] The lubricating oil composition of the present disclosure may contain one or more performance additives that can impart or improve any desired properties of the lubricating oil composition. Any additives known to those skilled in the art can be used in the lubricating oil composition disclosed herein. Some suitable additives have been described in R.M. Mortier et al., "Chemistry and Technology of Lubricants", 3rd Edition, Springer (2010) and L.R. Rudnik, "Lubricant Additives: Chemistry and Applications", 2nd Edition, CRC Press (2009).

[0068] Generally speaking, when in use, the concentration of each additive in the lubricating oil composition can be in the range of 0.001 to 10% by weight (such as 0.01 to 5% by weight or 0.05 to 2.5% by weight) of the lubricating oil composition. Including diluent oil, each additive in the lubricating oil composition can be in the range of 0.5 - 45% by weight (for example, 1.0 to 45% by weight, 5.0 to 40% by weight, 10 to 35% by weight, 20 to 32% by weight or 25 to 30% by weight) of the lubricating oil composition. In addition, the total amount of additives in the lubricating oil composition can be in the range of 0.001 to 20% by weight (such as 0.01 to 15% by weight or 0.1 to 10% by weight) of the lubricating oil composition. Including diluent oil, the total amount of additives in the lubricating oil composition can be in the range of 0.5 to 78% by weight (for example, 1.0 to 78% by weight, 5.0 to 78% by weight, 10 to 78% by weight, 20 to 78% by weight, 30 to 78% by weight or 45 to 78% by weight) of the lubricating oil composition.

[0069] As an example, the lubricating oil composition of the present invention may contain one or more lubricating oil performance additives, including detergents, dispersants, antiwear agents, antioxidants, friction modifiers, corrosion inhibitors, rust inhibitors, demulsifiers, foam inhibitors, viscosity modifiers, pour point depressants, nonionic surfactants, thickeners, etc. Some will be discussed in more detail below.

[0070] Detergent

[0071] The lubricating oil composition of the present disclosure may include one or more detergents. Detergents are additives that reduce the formation of piston deposits (such as high-temperature varnishes and lacquer deposits in engines). Detergents generally have the property of neutralizing acids and are capable of keeping finely divided solids in suspension. Most detergents are metal salts of acidic organic compounds.

[0072] Metal-containing or ash-forming detergents can be used both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents typically include a polar head and a long hydrophobic tail. The polar head contains a metal salt of an acidic organic compound.

[0073] In the art, detergents are generally referred to as neutral or overbased. A detergent containing substantially stoichiometric amounts of metal salts is typically described as a normal or neutral detergent. In embodiments where a large amount of metal base is incorporated into the detergent by reacting an excess of a metal compound (e.g., an oxide or hydroxide) with an acidic gas (e.g., carbon dioxide), the detergent is referred to as overbased.

[0074] Overbased metal detergents are typically produced by carbonating (using CO2) a mixture of a hydrocarbon, a detergent acid (e.g., a sulfonic acid or carboxylate), a metal oxide or hydroxide (e.g., calcium oxide or calcium hydroxide), and a promoter such as xylene, methanol, and water. For example, to prepare overbased calcium sulfonate, during the carbonation process, calcium oxide or calcium hydroxide reacts with gaseous carbon dioxide to form calcium carbonate. The sulfonic acid is neutralized with an excess of CaO or Ca(OH)2 to form a sulfonate.

[0075] Overbased detergents can be further characterized as low overbased, medium overbased, or high overbased. A low overbased detergent can be, for example, an overbased salt with a TBN below 100. In one embodiment, the TBN of the low overbased salt can be from about 5 to about 80. In another embodiment, the TBN of the low overbased salt can be from about 10 to about 80. In yet another embodiment, the TBN of the low overbased salt can be from about 10 to about 50.

[0076] A medium overbased detergent can be, for example, an overbased salt with a TBN of about 100 to about 250. In one embodiment, the TBN of the medium overbased salt can be from about 100 to about 200. In another embodiment, the TBN of the medium overbased salt can be from about 125 to about 175.

[0077] A high overbased detergent can be, for example, an overbased salt with a TBN above 250. In one embodiment, the TBN of the high overbased salt can be from about 250 to about 800.

[0078] Compounds that can be used in detergents include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates of metals, and other oil-soluble carboxylates, the metal being especially an alkali metal or an alkaline earth metal such as barium, sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, which may both be present in detergents used in lubricants, and mixtures of calcium and / or magnesium with sodium.

[0079] In one embodiment, the detergent can be one or more alkali metal salts or alkaline earth metal salts of alkyl-substituted hydroxyaromatic carboxylic acids and is a carboxylate or salicylate. Suitable hydroxyaromatic compounds include mononuclear monohydroxy and polyhydroxy aromatic hydrocarbons having 1 to 4, preferably 1 to 3, hydroxyl groups.

[0080] Suitable hydroxyaromatic compounds include phenol, catechol, resorcinol, hydroquinone, pyrogallol, cresol, etc. In certain embodiments, the preferred hydroxyaromatic compound is phenol.

[0081] The alkyl-substituted moiety of the alkali metal salt or alkaline earth metal salt of the alkyl-substituted hydroxyaromatic carboxylic acid can be derived from an α-olefin having 10 to 80 carbon atoms. The olefin employed can be straight-chain, isomerized straight-chain, branched, or partially branched straight-chain. The olefin can be a mixture of straight-chain olefins, a mixture of isomerized straight-chain olefins, a mixture of branched olefins, a mixture of partially branched straight-chain olefins, or a mixture of any of the foregoing.

[0082] In some embodiments, the mixture of straight-chain olefins is a mixture of normal α-olefins selected from olefins having 10 to 40 carbon atoms per molecule. In one embodiment, at least one of a solid or liquid catalyst is used to isomerize the normal α-olefins.

[0083] In some embodiments, at least about 75 mole % (e.g., at least about 80 mole %, at least about 85 mole %, at least about 90 mole %, at least about 95 mole %, or at least about 99 mole %) of the alkyl groups (such as the alkyl groups of the alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid detergent) contained in the alkali metal salt or alkaline earth metal salt of the alkyl-substituted hydroxyaromatic carboxylic acid are C 20 or higher alkyl substituents. In certain of these embodiments, the alkali metal salt or alkaline earth metal salt of the alkyl-substituted hydroxyaromatic carboxylic acid is the alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid derived from an alkyl-substituted hydroxybenzoic acid, wherein the alkyl group is a residue of a normal α-olefin containing at least 75 mole % C 20 to C 28 normal α-olefins. In another embodiment, at least about 50 mole % (e.g., at least 60 mole %, at least 70 mole %, at least 80 mole %, at least 85 mole %, at least 90 mole %, at least 95 mole %, or at least 99 mole %) of the alkyl groups of the alkali metal salt or alkaline earth metal salt of the alkyl-substituted hydroxybenzoic acid are C 20 to C 24 alkyl substituents.

[0084] In another embodiment, at least about 50 mole percent (e.g., at least 60 mole percent, at least 70 mole percent, at least 80 mole percent, at least 85 mole percent, at least 90 mole percent, at least 95 mole percent, or at least 99 mole percent) of the alkyl groups of the alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid are C 14 to C 18 alkyl substituents. In another embodiment, the alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid is derived from an alkyl group having isomerized C 10 -C 40 normal alpha olefin, isomerized C 20 -C 28 normal alpha olefin, or preferably isomerized C 20 -C 24 normal alpha olefin. In one embodiment, the alpha olefin isomerization level of the isomerized normal alpha olefin is between about 0.1 and about 0.4. In another embodiment, the alkyl group is derived from at least two alkylphenols. The alkyl group on at least one of the at least two alkylphenols is derived from an isomerized alpha olefin. The alkyl group on the second alkylphenol may be derived from a branched or partially branched olefin, a highly isomerized olefin, or a mixture thereof.

[0085] The alkyl-substituted moiety of the alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid may be derived from cashew nut shell liquid (CNSL) or hydrodistilled CNSL. Distilled CNSL is a mixture of biodegradable meta-alkyl-substituted phenols, where the alkyl groups are straight-chain and unsaturated, including cardanol. Catalytic hydrogenation of distilled CNSL yields a mixture of meta-alkyl-substituted phenols that is predominantly rich in 3-pentadecylphenol.

[0086] The alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid may be a mixture of ortho and para isomers. In one embodiment, the alkyl-substituted hydroxyaromatic carboxylic acid may contain from 1 to 99% ortho isomer and from 99 to 1% para isomer. In another embodiment, the alkyl-substituted hydroxyaromatic carboxylic acid may contain from about 5 to 70% ortho isomer and from 95 to 30% para isomer.

[0087] The alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid may be neutral or overbased. Generally, an overbased alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid is a salt in which the TBN of the alkali metal salt or alkaline earth metal salt of the alkyl-substituted hydroxyaromatic carboxylic acid has been increased by a method such as adding a base source (e.g., lime) and an acidic overbasing compound (e.g., carbon dioxide).

[0088] As noted, certain embodiments of the lubricant formulation may use one or more sulfonate detergents alone or in combination with other detergents. The sulfonates can be prepared from sulfonic acids, which can be obtained by sulfonation of alkyl-substituted aromatics (such as those obtained from petroleum fractionation) or by alkylation of aromatics. Examples of alkyl-substituted aromatic hydrocarbons that can be sulfonated include those obtained by alkylation of benzene, toluene, xylene, naphthalene, diphenyl, or their halogen derivatives. The alkylation can be carried out in the presence of a catalyst using an alkylating agent having from 3 to more than 70 carbon atoms. Alkaryl sulfonates typically contain from 9 to 80 or more carbon atoms, preferably 16 to 60, preferably 16 to 30, and most preferably 20 to 24 carbon atoms per alkyl-substituted aromatic moiety.

[0089] The oil-soluble sulfonates or alkaryl sulfonic acids can be neutralized with metal oxides, hydroxides, alkoxides, carbonates, carboxylates, sulfides, hydrosulfides, nitrates, borates, and ethers. The amount of the metal compound is selected according to the desired TBN of the final product.

[0090] Metal salts of phenols and sulfurized phenols (e.g., phenate or sulfurized phenate detergents) are prepared by reaction of a phenol or sulfurized phenol with a suitable metal compound such as an oxide or hydroxide. The sulfurized phenol can be prepared by reacting a phenol with sulfur or a sulfur-containing compound such as hydrogen sulfide, sulfur monohalide, or sulfur dihalide to form a product, which is typically a mixture of compounds in which two or more phenols are bridged by a sulfur-containing bridge. Additional details regarding the general preparation of sulfurized phenates can be found, for example, in U.S. Patent Nos. 2,680,096, 3,178,368, and 3,801,507, the contents of which are incorporated herein by reference.

[0091] The sulfur used to form the sulfurized compound can have any allotropic form of sulfur. The sulfur can be present as molten sulfur or as a solid (e.g., powder or granules) or as a solid suspension in a compatible hydrocarbon liquid.

[0092] In some embodiments, it is desirable to use calcium hydroxide as the calcium base because of its handling convenience relative to, for example, calcium oxide, and also because it provides excellent results. Other calcium bases, such as calcium alkoxides, can also be used.

[0093] Suitable alkylphenols that can be used are those in which the alkyl substituent contains a sufficient number of carbon atoms to render the resulting alkylphenate (e.g., overbased sulfurized alkylphenol calcium) composition oil-soluble. The oil-solubility can be provided by a single long-chain alkyl substituent or by a combination of alkyl substituents. Generally, the alkylphenols used will be different alkylphenols (e.g., C 20 to C 24A mixture of alkylphenols). In one embodiment, suitable alkylphenolic compounds will be derived from isomerized normal alpha-olefin alkyl groups having from about 10 to about 40 carbon atoms per molecule, with an isomerization level of the alpha-olefin of about 0.1 to about 0.4. In one embodiment, the isomerized normal alpha-olefin has from about 20 to about 24 carbon atoms. In one embodiment, suitable alkylphenolic compounds will be derived from alkyl groups that are branched olefinic propylene oligomers having from about 9 to about 80 carbon atoms or mixtures thereof. In one embodiment, the branched olefinic propylene oligomer or mixture thereof has from about 9 to about 40 carbon atoms. In one embodiment, the branched olefinic propylene oligomer or mixture thereof has from about 9 to about 18 carbon atoms. In one embodiment, the branched olefinic propylene oligomer or mixture thereof has from about 9 to about 12 carbon atoms.

[0094] In one embodiment, suitable alkylphenolic compounds include distilled cashew nut shell liquid (CNSL) or hydrogenated distilled CNSL. Distilled CNSL is a mixture of biodegradable meta-alkyl-substituted phenols where the alkyl groups are straight-chain and unsaturated, including cardanol. Catalytic hydrogenation of distilled CNSL produces a mixture of meta-alkyl-substituted phenols that are predominantly rich in 3-pentadecylphenol.

[0095] The alkylphenol can be a p-alkylphenol, m-alkylphenol, or o-alkylphenol. In certain embodiments, such as when an overbased product is desired, the alkylphenol is preferably predominantly p-alkylphenol, where no more than about 45 mole % of the alkylphenol is o-alkylphenol; and more preferably, no more than about 35 mole % of the alkylphenol is o-alkylphenol. Alkyl-hydroxy toluene or xylene can also be used, as well as other alkylphenols having one or more alkyl substituents in addition to at least one long-chain alkyl substituent. In the case of distilled cashew nut shell liquid, catalytic hydrogenation of distilled CNSL produces a mixture of meta-alkyl-substituted phenols.

[0096] Generally, the choice of alkylphenol can be based on the properties desired for the marine engine lubricant composition, particularly TBN, and oil solubility. Additional information regarding the preparation of suitable alkylphenols can be found, for example, in U.S. Patent Nos. 5,024,773, 5,320,763, 5,318,710, and 5,320,762, each of which is incorporated herein by reference.

[0097] Generally, based on the total weight of the marine lubricant composition, the amount of detergent can be from about 0.001 wt% to about 50 wt%, or from about 0.05 wt% to about 25 wt%, or from about 0.1 wt% to about 20 wt%, or from about 0.01 wt% to about 15 wt%.

[0098] The detergent may also include "mixed" or "complex" detergents formed with a mixed surfactant system that includes phenate and / or sulfonate components, such as phenate / salicylate, sulfonate / phenate, sulfonate / salicylate, sulfonate / phenate / salicylate, as described, for example, in U.S. Pat. Nos. 6,429,178, 6,429,179, 6,153,565. The detergent may also include a methylene-bridged polyphenol composition prepared by the reaction of phenol with formaldehyde or its reversible polymer, optionally sulfiding the methylene-bridged intermediate and then reacting the intermediate with an excess of metal base to produce a methylene-bridged polyphenol phenate composition. In one embodiment, the methylene-bridged polyphenol phenate composition may be further reacted with an epoxide. In one embodiment, the methylene-bridged polyphenol phenate composition is not sulfided.

[0099] Other detergents may be present in any suitable amount, such as from 0.1 to 45 wt%, or 0.5 to 30 wt% of the lubricating oil composition.

[0100] Dispersant

[0101] The lubricating oil compositions of the present disclosure may include one or more dispersants. During engine operation, oil-insoluble oxidation by-products are produced. Dispersants help keep these by-products in solution, thereby reducing their deposition on metal surfaces. Dispersants are commonly referred to as ashless dispersants because they do not contain ash-forming metals prior to being mixed in the lubricating oil composition and generally do not produce any ash when added to the lubricant. Ashless dispersants are characterized by polar groups attached to relatively high molecular weight or weight hydrocarbon chains. Typical ashless dispersants include N-substituted long-chain alkenyl succinimides. Examples of N-substituted long-chain alkenyl succinimides include polyisobutylene succinimides, the number average molecular weight of whose polyisobutylene substituents is in the range of 500 to 5000 daltons (e.g., 900 to 2500 daltons). The succinimide dispersants and their preparation are disclosed, for example, in U.S. Patent Nos. 4,234,435 and 7,897,696. Succinimide dispersants are generally imides formed from polyamines (usually poly(ethyleneamine)).

[0102] In some embodiments, the lubricant composition comprises at least one polyisobutylene succinimide dispersant derived from polyisobutylene having a number average molecular weight in the range of 500 to 5000 daltons (e.g., 900 to 2500 daltons). The polyisobutylene succinimide may be used alone or in combination with other dispersants.

[0103] Dispersants may also be post-treated by conventional methods by reaction with any of a variety of reagents. Among these reagents are boron compounds (e.g., boric acid) and cyclic carbonates (ethylene carbonate).

[0104] Another class of dispersants includes Mannich bases. Mannich bases are materials formed by the condensation of alkyl-substituted phenols of relatively high molecular weight, polyalkylene polyamines, and aldehydes such as formaldehyde. Mannich bases are described in more detail in U.S. Patent No. 3,634,515.

[0105] Another class of dispersants includes high molecular weight esters, which are prepared by the reaction of a hydrocarbyl acylating agent and a polyhydroxy aliphatic alcohol such as glycerol, pentaerythritol, or sorbitol. Such materials are described in more detail in U.S. Patent No. 3,381,022.

[0106] Another class of dispersants includes high molecular weight ester amides.

[0107] The dispersant may be present in the lubricating oil composition in an amount of 0.1 to 15% by weight.

[0108] Antiwear agent

[0109] Antiwear agents reduce friction and excessive wear and are generally based on compounds containing sulfur or phosphorus or both. Of note are metal salts of dialkyldithiophosphates, where the metal can be an alkali metal or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel, copper, or zinc. Zinc dialkyldithiophosphate (ZDDP) is an oil-soluble salt of dialkyldithiophosphoric acid and can be represented by the following formula:

[0110] Zn[SP(S)(OR)(OR')]2

[0111] where R and R′ may be the same or different hydrocarbyl groups containing from 1 to 18 (e.g., 2 to 12) carbon atoms. To obtain oil solubility, the total number of carbon atoms in the dithiophosphate (i.e., R and R′) will generally be 5 or greater.

[0112] The antiwear agent may be present in the lubricating oil composition in an amount of 0.1 to 6% by weight.

[0113] Antioxidant

[0114] Antioxidants slow the oxidative degradation of the base oil during use. Such degradation can lead to the presence of deposits, sludge on metal surfaces, or an increase in the viscosity of the lubricant.

[0115] Useful antioxidants include hindered phenols. Hindered phenol antioxidants typically contain secondary butyl and / or tertiary butyl groups as steric hindrance groups. The phenolic group may be further substituted with a hydrocarbon group (usually a straight-chain or branched-chain alkyl group) and / or a bridging group attached to a second aromatic group. Examples of hindered phenol antioxidants include 2,6-di-tert-butylphenol, 2,6-di-tert-butylcresol, 2,4,6-tri-tert-butylphenol, 2,6-dialkyl-phenol propionate derivatives, and bisphenols such as 4,4'-bis(2,6-di-tert-butylphenol) and 4,4'-methylene-bis(2,6-di-tert-butylphenol).

[0116] Sulfurized alkylphenols and their alkali metal salts and alkaline earth metal salts can also be used as antioxidants.

[0117] Non-phenolic antioxidants that can be used include aromatic amine antioxidants such as diarylamines and alkylated diarylamines. Specific examples of aromatic amine antioxidants include N-phenyl-2-naphthylamine, 4,4'-dioctyldiphenylamine, butylated / octylated diphenylamine, nonylated diphenylamine, and octylated N-phenyl-2-naphthylamine.

[0118] The antioxidant can be present in the lubricating oil composition in an amount of 0.01 to 15.0% by weight.

[0119] Friction modifier

[0120] A friction modifier is any material that is capable of changing the coefficient of friction of a surface lubricated by any lubricant or fluid containing such a material. Suitable friction modifiers can include fatty amines, esters such as borated glycerides, fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, or fatty imidazolines, as well as condensation products of carboxylic acids and polyalkylene-polyamines. As used herein, the term "fatty" associated with a friction modifier refers to a carbon chain having 10 to 22 carbon atoms, typically a straight carbon chain. Molybdenum compounds are also referred to as friction modifiers. The amount of the friction modifier present can be 0.01 to 10.0% by weight of the lubricating oil composition.

[0121] Rust inhibitor

[0122] Rust inhibitors typically protect lubricated metal surfaces from chemical attack by water or other contaminants. Suitable rust inhibitors can include suitable nonionic rust inhibitors, including nonionic polyoxyalkylene reagents (e.g., polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyethylene glycol monooleate); stearic acid and other fatty acids; dicarboxylic acids; metal soaps; fatty acid amine salts; metal salts of heavy sulfonic acids; partial carboxylic acid esters of polyols; phosphate esters; (short-chain) alkenyl succinic acids, their partial esters, and their nitrogen-containing derivatives; and synthetic alkylaryl sulfonates (e.g., metal dinonylnaphthalene sulfonates). Such additives can be present in the lubricating oil composition in an amount of 0.01 to 5% by weight.

[0123] Demulsifiers

[0124] Demulsifiers facilitate the oil-water separation in lubricating oil compositions exposed to water or steam. Suitable demulsifiers include trialkyl phosphates, as well as various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures thereof. Such additives can be present in the lubricating oil composition in an amount of 0.01 to 5% by weight.

[0125] Foam inhibitors

[0126] Foam inhibitors retard the formation of stable foams. Siloxanes and organic polymers are typical foam inhibitors. For example, polysiloxanes, such as silicone oil or polydimethylsiloxane, provide foam-inhibiting properties. Additional foam inhibitors include copolymers of ethyl acrylate and 2-ethylhexyl acrylate and optionally vinyl acetate. Such additives can be present in the lubricating oil composition in an amount of 0.001 to 1% by weight.

[0127] Viscosity modifiers

[0128] Viscosity modifiers provide high-temperature and low-temperature operability to lubricants. These additives impart shear stability at high temperatures and an acceptable viscosity at low temperatures. Suitable viscosity modifiers can include polyolefins, olefin copolymers (OCP), ethylene / propylene copolymers, polyisobutylene, hydrogenated styrene-isoprene polymers, styrene / maleate copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, α-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, and hydrogenated alkenyl aryl conjugated diene copolymers. Such additives can be present in the lubricating oil composition in an amount of 0.1 to 15% by weight.

[0129] Pour point depressants

[0130] Pour point depressants lower the lowest temperature at which a fluid will flow or be pourable. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyacrylamides, condensation products of halogenated paraffins and aromatic compounds, carboxylic acid vinyl ester polymers, and terpolymers of dialkyl fumarates, vinyl esters of fatty acids, and allyl vinyl ethers. Such additives can be present in the lubricating oil composition in an amount of 0.01 to 1.0 wt%.

[0131] Nonionic surfactants

[0132] Nonionic surfactants such as alkylphenols can improve asphaltene handling during engine operation. Examples of such materials include alkylphenols having an alkyl substituent from a straight-chain or branched-chain alkyl group having 9 to 30 carbon atoms. Other examples include alkylphenols, alkylnaphthols, and alkylphenol aldehyde condensates, where the aldehyde is formaldehyde such that the condensate is a methylene-bridged alkylphenol. Such additives can be present in the lubricating oil composition in an amount of 0.1 to 20 wt%.

[0133] Markers

[0134] The lubricating oil compositions of the present invention can contain a dye or marker component, such as a tracer, which is particularly useful for marking lubricants to protect brand assets, prevent misidentification, and assist in identifying leaks. The most useful types of markers or dyes are those that can be easily extracted, measured, and / or identified from the marked liquid. Many additives and tracers that have been proposed for or are currently used for marking or tagging lubricants include color and fluorescent dyes (e.g., diazo dyes, anthraquinone dyes, phthal dyes, etc.), radioactive substances, metal compounds or complexes (e.g., metal organic compounds, metal salts, metal oxides, metal coordination complexes, etc.), and various specific compounds that react with selected reagents to provide strongly colored derivatives.

[0135] Examples of markers include materials selected from the group consisting of barium sulfate, bismuth trioxide, iodine, iodides, titanium oxide, zirconium oxide, gold, platinum, silver, tantalum, niobium, stainless steel, and combinations thereof. Materials such as certain metal soaps, metal soaps of fatty acids, metal carboxylates, or known metal driers, which are supplied as solutions containing metals such as cobalt, lead, magnesium, titanium, zirconium, manganese, rhodium, platinum, aluminum, manganese, calcium, cerium, copper, nickel, vanadium, barium, tungsten, vanadium, and zinc, and mixtures thereof, can also be used as lubricant markers. Examples of zirconium-containing materials can include zirconium carboxylates such as zirconium 2-ethylhexanoate, zirconium octanoate, and zirconium salicylate materials.

[0136] Use of the lubricating oil composition

[0137] The lubricant composition can be effectively used as a cylinder lubricant, trunk piston engine oil, or system oil, etc. for compression ignition internal combustion engines (including marine engines, etc.).

[0138] The internal combustion engine can be a two-stroke or four-stroke engine.

[0139] In an embodiment, the internal combustion engine is a marine engine. In some embodiments, the marine engine can be a medium-speed four-stroke compression ignition engine with a speed of 250 to 1100 rpm or a low-speed crosshead two-stroke compression ignition engine with a speed of 200 rpm or lower (e.g., 60 to 200 rpm).

[0140] The marine engine can be lubricated with marine cylinder lubricant (usually in two-stroke engines), system oil (usually in two-stroke engines), or crankcase lubricant (usually for four-stroke engines).

[0141] The term "marine" does not limit the engine to those used in waterborne vessels; as understood in the art, it also includes those for other industrial applications, such as auxiliary power generation for main propulsion and stationary land-based engines for power generation.

[0142] In some embodiments, the internal combustion engine can be fueled with residual fuel, marine residual fuel, low-sulfur marine residual fuel, marine distillate fuel, low-sulfur marine distillate fuel, or high-sulfur fuel.

[0143] The internal combustion engine can also be operated with "gaseous fuels", such as methane-based fuels (e.g., natural gas), biogas, landfill gas, wood gas, gasified liquefied gas, gasified liquefied natural gas (LNG), or non-carbon-based gaseous fuels (e.g., ammonia, hydrogen).

[0144] Examples

[0145] The following illustrative examples are intended to be non-limiting.

[0146] The following components are used in the formulation of the marine lubricant composition of the examples. Generally, the marine lubricant composition of the examples includes an oil with lubricating viscosity (base oil component), a thickener, and an additive package.

[0147] The base oil components used in the formulation of the examples include:

[0148] XOM 150N: ExxonMobil Group I lubricating oil of 150N, with a KV of 5.1 mm2 / s at 100 °C

[0149] XOM 600N: ExxonMobil 600N: Group I lubricating oil with a KV of 12.4 mm2 / s at 100 °C

[0150] XOM 2500BS: ExxonMobil 2500BS: Group I lubricating oil with a KV of 30.6 mm2 / s at 100 °C

[0151] RLOP 100R: Chevron 100R Group II lubricating oil with a KV of 4.4 mm2 / s at 100 °C

[0152] RLOP 220R: Chevron 220RLOP: Group II lubricating oil with a KV of 6.4 mm2 / s at 100 °C

[0153] RLOP 600R: Chevron 600R RLOP: Group II lubricating oil with a KV of 12.0 mm2 / s at 100 °C

[0154] PIB-1: 2300 MW polyisobutene

[0155] PIB-2: 1000 MW polyisobutene

[0156] The additive packages used in the example formulations include:

[0157] Additive package A: an oil concentrate of 1.0 wt% calcium sulfonate detergent of 420BN (40.0 wt% diluent oil), an oil concentrate of 6.0 wt% calcium sulfonate detergent of 17BN (50.0 wt% diluent oil), an oil concentrate of 9.0 wt% calcium sulfide phenate detergent of 95BN derived from C20 to C24 isomerized alpha olefins (20.0 wt% diluent oil), an oil concentrate of 0.2 wt% polyisobutene succinimide dispersant, 1.5 wt% antioxidant, 0.1 wt% foam inhibitor, and 1.0 wt% diluent oil.

[0158] Additive package B: an oil concentrate of 3.0 wt% overbased calcium sulfide phenate detergent of 260BN derived from C20 to C24 isomerized alpha olefins (40.0 wt% diluent oil), an oil concentrate of 0.3 wt% overbased calcium carboxylate detergent of 410BN derived from C20 to C24 isomerized alpha olefins (33.0 wt% diluent oil), an oil concentrate of 2.9 wt% overbased calcium carboxylate detergent of 180BN derived from C20 to 24 isomerized normal alpha olefins (20 wt% diluent oil), an oil concentrate of 3.5 wt% polyisobutene succinimide dispersant, 1.5 wt% antioxidant, 0.1 wt% foam inhibitor, and 0.4 wt% diluent oil.

[0159] Additive Package C: An oil concentrate of a 410BN overbased calcium carboxylate detergent derived from C20 to C24 isomerized alpha-olefins (33.0 wt% diluent oil) at 7.5 wt%, an oil concentrate of an 180BN overbased calcium carboxylate detergent derived from C20 to C24 isomerized alpha-olefins (20.0 wt% diluent oil) at 5.2 wt%, zinc secondary dithiophosphate at 0.7 wt%, and a foam inhibitor at 0.1 wt%.

[0160] Additive Package D: An oil concentrate of a 95BN calcium sulfonate phenate detergent derived from C20 to C24 isomerized alpha-olefins (20.0 wt% diluent oil) at 0.6 wt%, an oil concentrate of a 410BN overbased calcium carboxylate detergent derived from C20 to C24 isomerized alpha-olefins (33.0 wt% diluent oil) at 1.1 wt%, zinc primary dithiophosphate at 0.6 wt%, a foam inhibitor at 0.02 wt%, and a diluent oil at 0.1 wt%.

[0161] Additive Package E: An oil concentrate of a 420BN calcium sulfonate detergent (40.0 wt% diluent oil) at 8.0 wt%, an oil concentrate of a 17BN calcium sulfonate detergent (50.0 wt% diluent oil) at 2.0 wt%, an oil concentrate of a 95BN calcium sulfonate phenate detergent derived from C20 to C24 isomerized alpha-olefins (20.0 wt% diluent oil) at 5.0 wt%, an oil concentrate of a polyisobutylene succinimide dispersant at 0.2 wt%, an antioxidant at 1.5 wt%, a foam inhibitor at 0.1 wt%, and a diluent oil at 0.9 wt%.

[0162] Additive Package F: An oil concentrate of a 420BN calcium sulfonate detergent (40.0 wt% diluent oil) at 7.8 wt%, an oil concentrate of a 17BN calcium sulfonate detergent (50.0 wt% diluent oil) at 2.0 wt%, an oil concentrate of a 260BN calcium sulfonate phenate detergent derived from propylene tetramer (30.0 wt% diluent oil) at 1.0 wt%, a 116BN calcium sulfonate phenate derived from propylene tetramer (40.0 wt% diluent oil) at 3.0 wt%, an oil concentrate of a polyisobutylene succinimide dispersant at 0.2 wt%, an antioxidant at 1.5 wt%, a foam inhibitor at 0.1 wt%, and a diluent oil at 0.9 wt%.

[0163] Additive Package G: an oil concentrate of 420BN calcium sulfonate detergent (40.0 wt% diluent oil) at 6.9 wt%, an oil concentrate of 17BN calcium sulfonate detergent (50.0 wt% diluent oil) at 6.0 wt%, an oil concentrate of 95BN calcium sulfonate phenate detergent derived from C20 to C24 isomerized alpha olefins (20.0 wt% diluent oil) at 9.0 wt%, an oil concentrate of polyisobutylene succinimide dispersant at 0.2 wt%, an antioxidant at 1.5 wt%, a foam inhibitor at 0.1 wt%, and a diluent oil at 1.3 wt%.

[0164] The degree of oxidation stability of the following examples was evaluated using the following tests. The results for each example are listed in Tables 2 to 6.

[0165] Test method

[0166] DSC Oxidation Test

[0167] According to ASTM D-6186, the DSC test was used to evaluate the thin-film oxidation stability of the test oil. During the test, the heat flow of the test oil flowing into and out of the sample cup was compared with that of the reference cup. The oxidation onset temperature is the temperature at which the test oil starts to oxidize. The oxidation induction time is the time at which the test oil starts to oxidize. A longer oxidation induction time means better performance. The oxidation reaction is exothermic and is clearly shown by the heat flow. The oxidation induction time was calculated to evaluate the thin-film oxidation stability of the test oil.

[0168] The DSC oxidation test can also be used to evaluate the deposit control performance of lubricants because the oxidation products generated during engine operation tend to form deposits. Therefore, higher oxidation stability can generally be associated with reduced deposit formation.

[0169] Petroleum Institute of America 48 (MIP-48) Test

[0170] The MIP-48 test consists of a thermal part and an oxidation part. During both parts of the test, the test samples are heated. In the thermal part of the test, nitrogen gas is passed through the heated oil sample for 24 hours, and in parallel, during the oxidation part of the test, air is passed through the heated oil sample for 24 hours. The samples are cooled, and the viscosities of both samples are determined. The viscosity increase of the test oil caused by oxidation is determined and corrected for the thermal effect. The oxidation-based viscosity increase of each marine lubricating oil composition is calculated by subtracting the kinematic viscosity of the air-blowing sample at 200 °C from the kinematic viscosity of the nitrogen-blowing sample at 200 °C and dividing the resulting difference by the kinematic viscosity of the nitrogen-blowing sample at 200 °C. This is done to correct for potential evaporation effects or any other thermal effects during the test and thus focus on the effect of oxidation. This correction may result in negative values. Test oils that exhibit better stability in the oxidation-based viscosity increase will result in lower absolute % values.

[0171] Result

[0172] Examples 1 and Comparative Example A

[0173] Examples 1 and Comparative Example A were formulated into marine cylinder lubricant compositions with a 15 BN, SAE 50 viscosity grade (KV of 18.5 cSt at 100 °C) containing 18.8 wt% of additive package A. Comparative Example A was formulated using a combination of heavy mineral oil Chevron RLOP600R and XOM 2500BS bright stock to achieve the appropriate lubricating oil viscosity. Example 1 contained a combination of light distillate mineral oil Chevron RLOP 220R and polyisobutene thickener to achieve the appropriate lubricating oil viscosity for the finished lubricant. The DSC oxidation test was used to evaluate the high-temperature oxidation stability of each lubricant. The results of each example are listed in Table 2 below.

[0174] Table 2

[0175]

[0176] The results listed in Table 2 show that the marine cylinder lubricant composition containing a combination of light distillate mineral oil and polyisobutene thickener exhibits surprisingly better oxidation performance than Comparative Example A. This is demonstrated by the longer oxidation induction time of Example 1 compared to Comparative Example A. Additionally, Example 1 was formulated to achieve an SAE 50 viscosity grade without using more conventional heavy neutral base oils and bright stocks in the finished lubricating oil composition.

[0177] Examples 2 and 3 and Comparative Examples B and C

[0178] Examples 2 and 3 and Comparative Examples B and C were formulated into marine cylinder lubricant compositions containing Additive Package E and Additive Package F at a 40BN, SAE 50 viscosity grade (KV at 100 °C of 18.5 cSt) (weight % in the following table). The finished lubricant for Comparative Examples B and C was formulated using a combination of heavy mineral oil and bright stock to achieve the appropriate lubricating oil viscosity. The finished lubricant for Examples 2 and 3 contained a combination of light distillate mineral oil Chevron RLOP 220R and polyisobutene thickener to achieve the appropriate lubricating oil viscosity. The DSC oxidation test was used to evaluate the oxidation stability of each lubricant. The results for each example are listed in Table 3 below.

[0179] Table 3.

[0180]

[0181] As shown in Table 3, the marine cylinder lubricant composition containing a combination of light neutral base oil and polyisobutene thickener surprisingly exhibited better oxidation performance than Comparative Examples B and C, as demonstrated by a higher oxidation induction time. Additionally, Examples 2 and 3 were formulated to achieve the SAE 50 viscosity grade without using conventional heavy lubricating oil and bright stock in the finished lubricant composition.

[0182] Examples 4 and 5 and Comparative Examples D and E

[0183] Examples 4 and 5 and Comparative Examples D and E were formulated into marine trunk piston engine oil (TPEO) compositions at 15BN and 40BN, SAE 40 viscosity grade (KV at 100 °C of 14.0 cSt). Examples 4 and Comparative Example D contained 11.7 wt% of Additive Package B and were formulated into 15BN TPEO. Examples 5 and Comparative Example E contained 13.5 wt% of Additive Package C and were formulated into 40BN TPEO. The finished lubricant for Comparative Examples D and E was formulated using a combination of heavy mineral oil and bright stock to achieve the appropriate lubricating oil viscosity. The finished lubricant for Examples 4 and 5 contained a combination of light distillate mineral oil Chevron RLOP 220R and polyisobutene thickener to achieve the appropriate lubricating oil viscosity. The DSC oxidation test was used to evaluate the oxidation stability of each lubricant. The results for each example are listed in Table 4 below.

[0184] Table 4.

[0185]

[0186] As shown in Table 4, the marine trunk piston engine lubricating oil composition containing a combination of a light neutral base oil and a polyisobutene thickener surprisingly exhibits superior oxidation performance compared to Comparative Examples B and C, as demonstrated by a higher oxidation induction time. Additionally, Examples 2 and 3 were formulated to achieve an SAE 50 viscosity grade without using conventional heavy lubricating oils and bright stocks in the finished lubricating oil composition.

[0187] Example 6 and Comparative Example F

[0188] Example 6 and Comparative Example F were formulated into a marine system lubricating oil composition with a 5BN, SAE 30 viscosity grade (KV at 100 °C of 11.5 cSt) containing 2.4 wt% of additive package D. Comparative Example F was formulated using the heavy mineral oil Chevron RLOP600R to achieve an appropriate lubricating oil viscosity. Example 6 contains a combination of a light distillate mineral oil Chevron RLOP220R and a polyisobutene thickener to achieve an appropriate lubricating oil viscosity for the finished lubricant. The DSC oxidation test was used to evaluate the high-temperature oxidation stability of each lubricant. The results for each example are listed in Table 5 below.

[0189] Table 5

[0190]

[0191] The results listed in Table 5 show that the marine system lubricating oil composition containing a combination of a light distillate mineral oil and a polyisobutene thickener surprisingly exhibits superior oxidation performance compared to Comparative Example F. This is demonstrated by a higher oxidation induction time for Example 6 compared to Comparative Example F. Additionally, Example 6 was formulated to achieve an SAE 30 viscosity grade without using more conventional heavy neutral base oils and bright stocks in the finished lubricating oil composition.

[0192] Examples 7 and 8 and Comparative Example G

[0193] Examples 7 and 8 and Comparative Example G were formulated into a marine cylinder lubricating oil composition with a 40BN, SAE 50 viscosity grade (KV at 100 °C of 18.5 cSt) (wt% in the table below) containing additive package G. The finished lubricant for Comparative Example G was formulated using a combination of a heavy mineral oil and a bright stock to achieve an appropriate lubricating oil viscosity. The finished lubricants for Examples 7 and 8 each contain a combination of a light distillate mineral oil XOM Core 150N and a polyisobutene thickener to achieve an appropriate lubricating oil viscosity. The DSC oxidation test was used to evaluate the oxidation stability of each lubricant. The results for each example are listed in Table 6 below.

[0194] Table 6.

[0195]

[0196] As shown in Table 6, the marine cylinder lubricant composition containing the combination of the light neutral base oil XOM 150N and the polyisobutene thickener surprisingly exhibits oxidation performance superior to that of Comparative Example G, which is demonstrated by a higher oxidation induction time. Additionally, Examples 7 and 8 were formulated to achieve an SAE 50 viscosity grade without using conventional heavy lubricating oils and bright stocks in the finished lubricant composition.

[0197] The above specific embodiments have been shown by way of example, and it should be understood that these embodiments can be readily generated in various modified and alternative forms and can also be used in any suitable combination. It should also be understood that the claims are not intended to be limited to the specific forms disclosed, but rather cover all modified forms, equivalent forms, and alternative forms falling within the spirit and scope of the present disclosure.

Claims

1. A marine engine lubricating oil composition, the marine engine lubricating oil composition comprising: (a) At least 40% by weight of an oil having a lubricating viscosity, said oil having a kinematic viscosity at 100 °C of 4.0 to less than 8.0 mm 2 / s; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 daltons; and wherein the marine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine lubricating oil composition is a single-grade lubricating oil composition that meets the requirements of the SAE J300 specification revised in January 2015 for SAE 20, SAE 30, SAE 40, SAE 50 or SAE 60 single-grade lubricating oils.

2. The composition according to claim 1, wherein the one or more polyisobutene thickeners have a number average molecular weight of 1,000 to 2,500 daltons.

3. The composition according to claim 1, wherein said one or more polyisobutene thickeners have a kinematic viscosity in the range of 630 to 2500 mm 2 / sec at 100 °C.

4. The composition according to claim 1, wherein the one or more polyisobutene thickeners are present in an amount of 4 to 40% by weight of the lubricating oil composition.

5. The composition according to claim 1, wherein the one or more polyisobutene thickeners are the only viscosity modifiers present in the lubricating oil composition.

6. The composition according to claim 1, wherein the lubricating oil composition does not contain bright stock.

7. The composition according to claim 1, wherein the lubricating oil composition has a sulfated ash content of 1.5% by weight or greater.

8. The composition according to claim 1, wherein the lubricating oil composition has a TBN of 10 to less than 70 mg KOH / g.

9. The composition according to claim 1, wherein the lubricating oil composition comprises a polyisobutene succinimide dispersant.

10. The composition according to claim 1, wherein the lubricating oil composition is a marine cylinder lubricating oil having a TBN of greater than 20 to less than 70 mg KOH / g.

11. The composition according to claim 1, wherein the lubricating oil composition is a marine trunk piston engine oil having a TBN of greater than 15 to 70 mg KOH / g.

12. The composition according to claim 1, wherein the lubricating oil composition is a marine system oil having a TBN of greater than 2 to 20 mg KOH / g.

13. A method of thickening a lubricating oil composition in a marine internal combustion engine, the method comprising adding to the engine a lubricating oil composition comprising: (a) At least 40% by weight of an oil having a lubricating viscosity, said oil having a kinematic viscosity at 100 °C of from 4.0 to less than 8.0 mm 2 / s; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 daltons; and wherein the marine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine lubricating oil composition is a single-grade lubricating oil composition that meets the requirements of the SAE J300 specification revised in January 2015 for SAE 20, SAE 30, SAE 40, SAE 50 or SAE 60 single-grade lubricating oils.

14. The method according to claim 13, wherein the one or more polyisobutene thickeners are present in an amount of 4 to 40% by weight of the lubricating oil composition.

15. The method according to claim 13, wherein the one or more polyisobutene thickeners are the only viscosity modifiers present in the lubricating oil composition.

16. The method according to claim 13, wherein the lubricating oil composition does not contain bright stock.

17. The method according to claim 13, wherein the lubricating oil composition has a sulfated ash content of 1.5 wt% or higher.

18. The method according to claim 13, wherein the lubricating oil composition has a TBN of 10 to less than 70 mg KOH / g.

19. The method according to claim 13, wherein the lubricating oil composition comprises a polyisobutene succinimide dispersant.

20. A method of controlling deposit formation in an internal combustion engine, the method comprising operating the internal combustion engine with a lubricating oil composition comprising: (a) At least 40% by weight of an oil having a lubricating viscosity, said oil having a kinematic viscosity at 100 °C of 4.0 to less than 8.0 mm 2 / s; and (b) one or more polyisobutene thickeners having a number average molecular weight of 400 to 6,000 daltons; and wherein the marine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine lubricating oil composition is a single-grade lubricating oil composition that meets the requirements of the SAE J300 specification revised in January 2015 for SAE 20, SAE 30, SAE 40, SAE 50, or SAE 60 single-grade lubricating oils.

21. The method according to claim 20, wherein the one or more polyisobutene thickeners are present in an amount of 4 to 40 wt% of the lubricating oil composition.

22. The method according to claim 20, wherein the one or more polyisobutene thickeners are the only viscosity modifiers present in the lubricating oil composition.

23. The method according to claim 20, wherein the lubricating oil composition does not contain bright stock.

24. The method according to claim 20, wherein the lubricating oil composition has a sulfated ash content of 1.5 wt% or higher.

25. The method according to claim 20, wherein the lubricating oil composition has a TBN of 10 to less than 70 mg KOH / g.

26. The method according to claim 20, wherein the lubricating oil composition comprises a polyisobutene succinimide dispersant.

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