Marine diesel engine cylinder lubricating oil composition

Abstract

A marine diesel engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of from 30,000 to 120,000. The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g. The marine diesel engine lubricating oil composition is a single-stage lubricating oil composition which meets the specification requirements of SAE J300 on SAE 40, SAE 50 or SAE 60 single-stage lubricating oil revised in January 2015.

Description

Technical Field

[0001] The present disclosure relates to lubricating oil compositions, and more particularly, to the use of olefin copolymer thickeners in marine cylinder lubricating oil compositions. Background Art

[0002] This section is intended to introduce the reader to various aspects of the technology that may be related to various aspects of the present disclosure described and / or claimed below. It is believed that this discussion helps to provide the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Therefore, it should be understood that these statements should be interpreted from this perspective, rather than as an admission of prior art.

[0003] Marine diesel internal combustion engines can generally be divided into low-speed, medium-speed or high-speed engines. Low-speed diesel engines are unique in size and operating methods. These engines are quite large and usually run in the range of about 60 to 200 revolutions per minute (rpm). Low-speed diesel engines run under a two-stroke cycle and are generally direct-connected and direct-commutated engines of a "crosshead" configuration, in which a diaphragm and one or more stuffing boxes separate the power cylinder from the crankcase to prevent combustion products from entering the crankcase and mixing with the crankcase oil. Marine two-stroke diesel cylinder lubricating oils must meet performance requirements to adapt to the harsh operating conditions required for more modern large-bore engines to operate 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 crankcase, which are referred to as cylinder lubricating oils and system oils, respectively. Marine cylinder lubricants have their own unique requirements.

[0004] In a two-stroke crosshead engine, the cylinders are lubricated in a total loss manner, with cylinder oil being sprayed onto each cylinder individually through lubricators positioned around the cylinder liner. The cylinder lubricant is not recirculated but is burned with the fuel. The cylinder lubricant needs to provide a strong film between the cylinder liner and the piston ring to fully lubricate the cylinder wall to prevent scuffing, and also needs to be thermally stable so that the lubricant does not form deposits on the hot surfaces of the piston and piston ring, and be able to neutralize sulfur-based acidic combustion products.

[0005] Recently, due to health and environmental concerns, regulations have mandated that marine diesel engines must use fuels with lower sulfur content. As a result, manufacturers are now designing marine diesel engines for use with a variety of fuels, including non-residual gaseous fuels (e.g., compressed or liquefied natural gas), high-quality distillate fuels, and poorer quality medium or heavy fuels, such as marine residual fuels, which typically have higher sulfur and higher asphaltene content. For non-residual fuel operation, the fuel does not contain a large amount of asphaltenes and has a much lower sulfur content. When low-sulfur fuels are burned, less acid is formed in the combustion chamber.

[0006] One of the main characteristics of a lubricant that helps protect marine diesel engines is the "thickness" of the lubricant film, i.e., viscosity. Lubricants used to lubricate marine diesel internal combustion engines have very high industry requirements for viscosity due to the low operating speeds and high loads, and are generally high viscosity single-grade (i.e., with little or no viscosity index improvement characteristics) lubricants of SAE 40, SAE 50 or SAE 60 viscosity grades. Because hydrocracking causes viscosity loss in the base stock, marine oils cannot usually be formulated using hydrocracked base stocks alone. In order to achieve the appropriate lubricant film thickness, conventional marine formulations usually include a large amount of 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 tower bottoms.

[0007] However, reliance on bright stock is not always desirable due to the presence of oxidatively unstable aromatic compounds. In addition, the supply of bright stock is also decreasing, resulting in the need to use alternative solutions to impart the required viscosity to the lubricant when bright stock is used in large quantities, such as those used in marine engines. Given the increasing severity of change as the design of modern marine engines changes, the changing requirements related to fuel quality, and the reduction in bright stock capacity, there is a continuing need for improved marine diesel engine cylinder lubricant formulation technology that provides improved performance while achieving the high viscosity required for marine cylinder lubricants. Summary of the invention

[0008] An overview of certain embodiments disclosed herein is as follows. It should be understood that these aspects presented are only intended to provide the reader with a brief overview of these specific embodiments, and these aspects are not intended to limit the scope of the present disclosure. In fact, the present disclosure may encompass a number of aspects that may not be described below.

[0009] As noted above, there is a continuing need for improved marine diesel engine cylinder lubricant formulation technology that provides improved performance while achieving the high viscosity required for marine cylinder lubricants. It is now recognized that these and other technical effects can be achieved by using suitable olefin copolymer thickeners in combination with light and / or heavy neutral base oils in marine cylinder lubricant formulations, examples of which are described herein.

[0010] For example, in one aspect, the present disclosure relates to a marine diesel engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000. The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a monograde lubricating oil composition that meets the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricating oils as revised in January 2015.

[0011] In another aspect, the present disclosure relates to a method for thickening a lubricating oil composition in a marine diesel internal combustion engine. The method comprises adding a lubricating oil composition to the engine, the lubricating oil composition comprising: (a) a major amount of an oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000. The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a monograde lubricating oil composition that meets the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricants as revised in January 2015.

[0012] In another aspect, the present disclosure relates to a method for 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) a major amount of an oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000. The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g and is a monograde lubricating oil composition that meets the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricants as revised in January 2015. DETAILED DESCRIPTION

[0013] definition

[0014] In this specification, the following words and expressions if and when used have the following ascribed meanings.

[0015] By "major amount" is meant greater than 40% by weight of the composition.

[0016] "Minor amount" means less than 40% by weight of the composition.

[0017] "Marine residual fuel" refers to a material combustible in large marine engines having a carbon residue of at least 2.5 wt % (e.g., at least 5 wt %, or at least 8 wt %) (relative to the total weight of the fuel) (as defined in International Organization for Standardization (ISO) 10370) and a viscosity at 50°C greater than 14.0 cSt, such as marine residual fuels as defined in International Organization for Standardization specification ISO 8217:2005, "Petroleum products--Fuels (class F)--Specifications of marine fuels", the contents of which are incorporated herein in their entirety.

[0018] "Residual fuel" refers to a fuel that complies with the residual marine fuel specification as set out in the ISO 8217:2010 international standard. "Low sulfur marine fuel" refers to a fuel that complies with the residual marine fuel specification as set out in the ISO 8217:2010 specification, and in addition has about 1.5 wt% or less, or even about 0.5 wt% or less, of sulfur relative to the total weight of the fuel.

[0019] "Distillate fuel" means a fuel that meets the specifications for distillate marine fuels as set forth in the ISO 8217:2010 international standard. "Low sulfur distillate fuel" means a fuel that meets the specifications for distillate marine fuels as set forth in the ISO 8217:2010 international standard, and in addition has about 0.1 wt% or less, or even about 0.005 wt% or less, of sulfur relative to the total weight of the fuel.

[0020] "Low sulfur fuel" refers to 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.

[0021] A "high sulfur fuel" is a fuel having greater than 1.5 weight percent sulfur relative to the total weight of the fuel.

[0022] The term "active based" refers to additive materials that are not diluent oils or solvents.

[0023] As used in this specification and 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 expressly stated otherwise. In the case of branched α-olefins, the branches may be at the 2-position (vinylidene) and / or 3-position or higher relative to the olefin double bond. Whenever used in this specification and 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 a mixture of isomers, and are usually also a mixture of compounds having a range of carbon numbers. Low molecular weight α-olefins, such as C6, C8, C 10 , C 12 and C 14 α-olefins, almost all 1-olefins. Higher molecular weight olefin fractions such as C 16 -C 18 or C 20 -C 24 The proportion of double bonds isomerized to internal or vinylidene positions increases

[0024] "Normal alpha olefin" (NAO) refers to a linear aliphatic monoolefin having a carbon-carbon double bond between a first and a second carbon atom. It should be noted that "normal alpha olefin" is not synonymous with "linear alpha olefin" because the term "linear alpha olefin" may include linear olefin compounds having a double bond between a first and a second carbon atom.

[0025] "Isomerized olefin" or "isomerized normal alpha olefin" refers to an olefin obtained by isomerizing an olefin. Typically, isomerized olefins have double bonds at different positions than the starting olefins from which they are derived, and may also have different characteristics.

[0026] "Isomerization level (I)" refers to the isomerization level measured by NMR methods. The isomerization level of olefins was determined by hydrogen-1 (1H) NMR. NMR spectra were obtained using TopSpin 3.2 spectral processing software at 400 MHz in chloroform-d on a Bruker Ultrashield Plus 400. The isomerization level represents the relative amount of methyl groups (-CH3) (chemical shift 0.30 to 1.01 ppm) attached to methylene backbone groups (-CH2-) (chemical shift 1.01 to 1.38 ppm) and is defined by equation (I) = m / (m+n), wherein m is the NMR integral of methyl groups with chemical shifts between 0.30 ± 0.03 and 1.01 ± 0.03 ppm, and n is the NMR integral of methylene groups with chemical shifts between 1.01 ± 0.03 and 1.38 ± 0.10 ppm.

[0027] The term "Total Base Number" or "TBN" or "BN" refers to the level of alkalinity in an oil sample according to ASTM Standard No. D2896 or equivalent procedures, which indicates the ability of the composition to continue to neutralize corrosive acids. The test measures the change in conductivity, and the results are expressed as mgKOH / g (milligram equivalents of KOH required to neutralize 1 gram of product). Therefore, a high TBN reflects a strongly overbased product, and therefore a higher reserve of base for neutralizing acids. Where TBN values ​​are introduced herein, it is understood that they are expressed in units of mgKOH / g.

[0028] "Overbased" is used to describe metal detergents in which the ratio of the number of equivalents of metal moiety to the number of equivalents of acid moiety is greater than one.

[0029] "Soap" refers to a neutral detergent compound which contains an approximately stoichiometric amount of a metal to effect neutralization of one or more acidic groups present in the organic acid used to prepare the detergent.

[0030] "Metal" refers to an alkali metal, an alkaline earth metal or a mixture thereof. When an alkali metal is used, the alkali metal is lithium, sodium or potassium. When an alkaline earth metal is used, the alkaline earth metal may be selected from the group consisting of calcium, barium, magnesium and strontium. Calcium and magnesium are preferred.

[0031] Unless otherwise expressly stated, "weight percent" (wt%) refers to the percentage of the total weight of the entire composition by which the component, compound or substituent is present. Unless otherwise stated, all reported percentages are based on the weight percent of the active ingredient (i.e., without regard to 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 mixtures thereof). The weight percents representing the combination of the component and the carrier or diluent oil are referred to as the weight percents "as is".

[0032] The term "sulfated ash content" refers to the amount of metal-containing additives (eg, calcium, magnesium, molybdenum, zinc) in a lubricating oil composition, and is generally measured according to ASTM D874, which is incorporated herein by reference.

[0033] Lubricating oil composition

[0034] It has been discovered that the use of suitable olefin copolymer thickeners in combination with light and / or heavy neutral base oils in marine lubricants can provide one or more surprising technical effects in marine cylinder lubricant compositions. These technical effects can include improving the resistance to deposit formation and oxidation stability when the engine is operating under various load conditions (such as high load conditions) while achieving appropriate lubricant viscosity.

[0035] In certain embodiments, the lubricating oil composition of the present disclosure is a marine diesel engine cylinder lubricating oil. In such embodiments, the lubricating oil composition includes (a) a major amount of oil having lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000; wherein the lubricating oil composition is a monograde lubricating oil composition that meets the specification requirements of SAE J300 for SAE 40, 50 or 60 monograde engine oils revised in January 2015, and has a TBN of less than 70 mg KOH / g as measured by ASTM D2896. The kinematic viscosity of the oil having lubricating viscosity may correspond to the viscosity of a heavy neutral oil or a light neutral oil.

[0036] The lubricating oil composition may be a monograde lubricating oil composition that complies with the SAE J300 specification for 40, 50 or 60 monograde engine oils as revised in January 2015. SAE 40 oils have a viscosity of 12.5 to <16.3 mm at 100°C. 2 / s kinematic viscosity. SAE 50 oil has a kinematic viscosity of 16.3 to <21.9 mm at 100°C. 2 / s kinematic viscosity. SAE 60 oil has a kinematic viscosity of 21.9 to <26.1 mm at 100°C. 2 / s kinematic viscosity.

[0037] In some embodiments, the lubricating oil composition is suitable for use as a marine cylinder lubricant (MCL).The marine cylinder lubricant of the present disclosure is manufactured according to SAE 40, SAE 50 or SAE 60 monograde specifications to provide a sufficiently thick lubricant film on the cylinder liner wall at high temperatures.

[0038] 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 sulfur-containing fuel being burned. This neutralization is usually achieved by including alkaline substances such as over-alkaline metal detergents. The neutralizing ability of an oil is characterized by its alkalinity and measured by its total base number (TBN). Typically, sulfur-containing fuels used to operate marine diesel engines require marine cylinder lubricants to have high detergency and neutralizing ability, even if the oil is only exposed to heat and other stresses in a short period of time. On the other hand, compared with sulfur-containing fuels, low-sulfur fuels may not require such a high neutralizing ability.

[0039] In order to allow sufficient neutralization and detergency while maintaining a relatively low level of deposits, the marine diesel engine cylinder lubricant of the present disclosure has a TBN of less than 70 mg KOH / g. For example, the TBN may 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 mg KOH / g, 50 to 5 mg KOH / g, 50 to 10 mg 120 KOH / g, 50 to 15 mg KOH / g, or 50 to 20 mg KOH / g. By way of further example, the TBN may 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.

[0040] 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 D 874. For example, the lubricating oil compositions of the present disclosure may have a sulfated ash level of 1.5 to 27 wt % as determined by ASTM D 874. By further example, the lubricating oil compositions of the present disclosure may 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.

[0041] Oil of lubricating viscosity

[0042] The lubricating oil composition of the present disclosure has at least 40 wt % of oil of lubricating viscosity, 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 %), based on the total weight of the composition. For example, the lubricating oil composition of the present disclosure may contain 40 wt % to 95 wt %, 50 wt % to 90 wt %, 55 wt % to 85 wt % of oil of lubricating viscosity. Oil of lubricating viscosity may also be referred to as base oil.

[0043] According to certain embodiments of the present disclosure, the oil having lubricating viscosity has a viscosity of 4.0 mm at 100°C. 2 / s to less than 8.5mm 2 / s kinematic viscosity. For example, an oil with lubricating viscosity may have a kinematic viscosity of 4.0 mm / s at 100°C. 2 / s to 8mm 2 / s, or 4.5mm 2 / s to 8mm 2 / s, or 5.0mm 2 / s to 7.5mm 2 / s kinematic viscosity.

[0044] According to another embodiment of the present disclosure, the oil having lubricating viscosity has a viscosity of 8.5 mm at 100°C. 2 / s to 15.0mm 2 / s kinematic viscosity. For example, an oil with lubricating viscosity may have a kinematic viscosity of 9.0 mm / s at 100°C. 2 / s to 14.0mm 2 / s, or 10.0mm 2 / s to 13.0mm 2 / s, or 10.0mm 2 / s to 12.0mm 2 / s kinematic viscosity.

[0045] In other embodiments, the oil of lubricating viscosity may include a mixture of two or more base oils. The first base oil in the mixture of two or more base oils has a viscosity of 8.5 mm at 100°C. 2 / s to 15.0mm 2 / s, for example 4.0mm 2 / s to 8mm 2 / s, or 4.5mm 2 / s to 8mm 2 / s, or 5.0mm 2 / s to 7.5mm 2 The second base oil in the mixture of two or more base oils may have a kinematic viscosity of 8.5 mm / s at 100°C. 2 / s to 15.0mm 2 / s, for example 9.0mm 2 / s to 14.0mm 2 / s, or 10.0mm 2 / s to 13.0mm 2 / s, or 10.0mm 2 / s to 12.0mm 2 / s kinematic viscosity.

[0046] The oil of lubricating viscosity of the present disclosure may include only one base oil component, or may include a mixture of two or more base oil components to achieve the above kinematic viscosity. The oil of lubricating viscosity may be selected from any one of the base oils of Groups I to V specified in the American Petroleum Institute (API) Base Oil Interchangeability Guide (API 1509). These five types of base oils are summarized in Table 1:

[0047] Table 1

[0048]

[0049] (1) ASTM D2007

[0050] (2) ASTM D2270

[0051] (3) ASTM D3120, ASTM D4294 or ASTM D4297

[0052] Class I, II and III are mineral oil base stocks.Class IV base oil contains real synthetic molecular substances, which are produced by the polymerization of olefinically unsaturated hydrocarbons.Many Class V base oils are also real synthetic products, and can include diesters, polyol esters, polyalkylene glycols, alkylated aromatic compounds, polyphosphates, polyvinyl ethers and / or polyphenylene oxides etc., but can also be naturally occurring oils, such as vegetable oils.It should be noted that although Class III base oils are derived from mineral oils, the strict processing of these fluid experiences makes their physical properties very similar to some real synthetic substances, such as PAO.Therefore, the oil derived from Class III base oil can be called synthetic fluid in the industry.

[0053] The base oil used in the disclosed lubricating oil composition can be a mineral oil, an animal oil, a vegetable oil, a synthetic oil or a mixture thereof. Suitable oils can be derived from hydrocracked, hydrogenated, hydrofined, unrefined, refined and re-refined oils and mixtures thereof.

[0054] Unrefined oils are those derived from natural, mineral or synthetic sources, with little or no further purification. Refined oils are similar to unrefined oils, except that they are treated in one or more purification steps, which may lead to improvements in one or more properties. Examples of suitable purification techniques are solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Refining to edible quality oils may or may not be useful. Edible oils may also be referred to as white oils. In some embodiments, the lubricating oil composition does not contain edible oils or white oils.

[0055] Re-refined oils are also known as reclaimed or reprocessed oils. These oils are obtained similarly to refined oils, using the same or similar processes. Typically, these oils are also processed by techniques involving the removal of spent additives and oil breakdown products.

[0056] Mineral oil can include oil obtained by drilling or oil obtained from plants and animals or any mixture thereof. Such oil can include castor oil, lard, olive oil, peanut oil, corn oil, soybean oil and linseed oil, and mineral lubricating oils, such as liquid petroleum and solvent-treated or acid-treated paraffin-type, naphthenic or mixed paraffin-naphthenic mineral lubricating oils. If desired, such oil can be partially or completely hydrogenated. Oil derived from coal or shale may also be useful.

[0057] Useful synthetic lubricating oils may include hydrocarbon oils such as polymeric, oligomeric or interpolymeric olefins (e.g., polybutene, polypropylene, propylene / isobutylene copolymers); trimers or oligomers of poly(1-hexene), poly(1-octene), 1-decene, such as poly(1-decene), such materials are generally referred to as alpha-olefins, and mixtures thereof; alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di-(2-ethylhexyl)-benzene); polyphenylenes (e.g., biphenyl, terphenyl, alkylated polyphenylenes); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers and alkylated diphenyl sulfides and derivatives, analogs and homologs thereof or mixtures thereof. Polyalphaolefins are typically hydrogenated materials.

[0058] Other synthetic lubricating oils include polyol esters, diesters, liquid esters containing phosphoric acid (e.g., tricresyl phosphate, trioctyl phosphate, and diethyl ester of decanephosphonic acid) or polymerized tetrahydrofuran. Synthetic oils can be prepared by Fischer-Tropsch reactions, and can typically be hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, oil can be prepared by Fischer-Tropsch gas-liquid synthesis procedures and other gas-liquid oils.

[0059] The base oil used in the formulated lubricating oil that can be used for the present disclosure is any one of the various oils corresponding to API Class I, Class II, Class III, Class IV and Class V oils and their mixtures. In one embodiment, the base oil is a Class II base oil or a blend of two or more different base oils. In another embodiment, the base oil is a Class I base oil or a blend of two or more different Class I base oils. Suitable Class I base oils include any light overhead fractions from a vacuum distillation tower, such as, for example, any light neutral, medium neutral and heavy neutral base oil stocks.

[0060] Base oils may also include residual base stocks or bottoms, such as bright stock. Bright stock is a high viscosity base oil that is usually produced from residual stocks or bottoms and is highly refined and dewaxed. Bright stock may have a viscosity greater than 180 mm at 40°C. 2 / s (for example, greater than 250mm 2 / s, or even between 500 and 1100 mm 2 In certain embodiments, the lubricating oil composition does not contain bright stock.

[0061] Thickener

[0062] According to an embodiment of the present invention, in order to obtain a finished lubricating oil composition having a desired viscosity grade, a thickener may be added to the lubricating oil composition to increase its viscosity. It has surprisingly been found that the use of a suitable olefin copolymer thickener in combination with a light and / or heavy neutral base oil can provide a lubricating oil composition that exhibits improved resistance to deposit formation and oxidation stability in an engine operating under high load conditions while achieving a suitable lubricating oil viscosity.

[0063] According to an embodiment of the present disclosure, suitable thickeners may include olefin copolymers (OCPs) as described herein. Based on active substances, such additives are generally present in 0.1% by weight or higher, for example, 0.1 to 12% by weight, of the lubricating oil composition. In certain embodiments, OCP is present in 0.2 to 10% by weight, 0.3 to 9% by weight, 0.4 to 8% by weight, or 0.5 to 7% by weight of the lubricating oil composition, based on active substances. In other embodiments, OCP is present in 0.5 to 12.0% by weight, 0.5 to 5% by weight, or 1 to 2% by weight of the lubricating oil composition, based on active substances. In other embodiments, OCP is present in 1.0% by weight or higher, for example, 1.0 to 12.0% by weight, 1.0 to 5% by weight, 1.3 to 4.5% by weight, 1.5 to 4.0% by weight, 2.0 to 12.0% by weight, or 2.0 to 3.5% by weight of the lubricating oil composition, based on active substances. In certain embodiments, the OCP is the only viscosity modifier or thickener present in the lubricating oil composition.

[0064] In certain embodiments, olefin copolymers are copolymers based on units of ethylene units and alpha-olefins (e.g., normal alpha-olefins, isomerized alpha-olefins), such as ethylene-propylene copolymer compositions. Other alpha-olefins suitable for replacing propylene or combining with ethylene and propylene to form terpolymers or tetrapolymers include, for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene; and branched alpha-olefins, such as 4-methyl-1-pentene, 4-methyl-1-hexene, 4-methylpentene-1,4,4-dimethyl-1-pentene, 6-methylheptene-1 and mixtures thereof.

[0065] Olefin copolymers according to certain embodiments of the present invention advantageously have a number average molecular weight of 30,000 to 120,000 g / mol, preferably 40,000 to 120,000 g / mol, more preferably 45,000 to 115,000 g / mol. In some embodiments, such molecular weights can balance useful thickening with stability of the formulation under stress. The combination of molecular weight and the above amounts can provide a viscosity suitable for a marine cylinder lubricant composition.

[0066] The shear stability index (SSI) of the olefin copolymer, ie, its resistance to mechanical degradation under shear stress, is from 5 to 50. In certain embodiments, the SSI is in the range of 15 to 50, such as 24 to 50, or 24 to 40.

[0067] The olefin copolymer according to certain embodiments of the present invention advantageously has an ethylene unit content in the range of 30 wt % to 80 wt %, preferably 30 wt % to 75 wt %, more preferably 49 wt % to 72 wt % relative to the weight of the olefin copolymer. The olefin copolymer according to the present invention also advantageously has an ethylene unit content in the range of 40 mol % to 90 mol %, preferably 40 mol % to 80 mol %, more preferably 50 mol % to 80 mol %, relative to the mole number of the olefin copolymer.

[0068] The olefin copolymer according to certain embodiments of the present invention can be a bimodal ethylene copolymer composition having a first ethylene copolymer fraction with a relatively low ethylene content; and a second ethylene copolymer fraction with a relatively high ethylene content. In one embodiment, the polymerization process for preparing the olefin copolymer may include reacting two or more α-olefin monomers (one of which is preferably ethylene; in some aspects, the other may be a C3-C 12 The olefin copolymer used in certain embodiments may include one or more olefin copolymers described in US20130203640, the disclosure of which is incorporated herein by reference in its entirety.

[0069] In some of these embodiments, the olefin copolymer composition of the present disclosure may include (a) a first ethylene-α-olefin copolymer and (b) a second ethylene-α-olefin copolymer. For example, the first ethylene-α-olefin copolymer (a) has an ethylene content of about 60 to about 80 weight %, and may be referred to as a "semi-crystalline" ethylene-α-olefin copolymer in this article. More typically, the ethylene content of the first ethylene-α-olefin copolymer is about 63 to about 77 weight %, and even more typically, the ethylene content of the first ethylene-α-olefin copolymer is about 65 to about 75 weight %. The second ethylene-α-olefin copolymer (b) has an ethylene content of less than about 60 weight %, more typically less than about 55 weight %, and even more typically about 42 to about 54 weight %, and is an ethylene-α-olefin copolymer with a lower crystallinity than the first ethylene-α-olefin copolymer (a), and may be referred to as an "amorphous" ethylene-α-olefin copolymer in this article.

[0070] The melt flow rate ratio (MFRR) of the first ethylene-α-olefin copolymer (a) (defined as the ratio of the MFR measured at 230°C / 21.6kg and at 230°C / 2.16kg) may be >30, and more typically up to about 55, even more typically from about 33 to about 45, preferably >34, more preferably from about 34 to about 45, and more preferably from about 35 to about 43. When the MFR condition is also observed, the MFR of the first ethylene-α-olefin copolymer (a) is at least about 1.5 g / 10min, and in another embodiment, the MFR is at least about 1.6 g / 10min. A more typical range of MFR is from about 1.5 g / 10min to about 6.5 g / 10min, and an even more typical range is from about 2.5 g / 10min to about 5.5 g / 10min. MFR is measured by ASTM D 1238 Condition L (230°C / 2.16kg). In one embodiment, the first ethylene-α-olefin copolymer (a) has a MFRR > 30 and a MFR of at least about 1.5 g / 10 min. More preferably, the first ethylene-α-olefin copolymer (a) has a MFRR > 34 and a MFR of at least about 1.6 g / 10 min.

[0071] In one embodiment, the olefin copolymer composition contains about 30% by weight to about 70% by weight of (a) and about 70% by weight to about 30% by weight of (b), based on the total amount of the first ethylene-α-olefin copolymer (a) and the second ethylene-α-olefin copolymer (b) in the composition. In another embodiment, the olefin copolymer composition contains about 40% by weight to about 60% by weight of (a) and about 60% by weight to about 40% by weight of (b), based on the total amount of the first ethylene-α-olefin copolymer (a) and the second ethylene-α-olefin copolymer (b) in the composition. In a specific embodiment, the olefin copolymer composition contains about 50% by weight to about 54% by weight of (a) and about 46% by weight to about 50% by weight of (b), based on the total amount of the first ethylene-α-olefin copolymer (a) and the second ethylene-α-olefin copolymer (b) in the composition.

[0072] In one embodiment, the weight average molecular weight of the first ethylene-α-olefin copolymer is from about 60,000 to about 120,000. In another embodiment, the weight average molecular weight of the first ethylene-α-olefin copolymer is from about 70,000 to about 110,000. In one embodiment, the weight average molecular weight of the second ethylene-α-olefin copolymer is from about 60,000 to about 120,000. In another embodiment, the weight average molecular weight of the second ethylene-α-olefin copolymer is from about 70,000 to about 110,000.

[0073] In one embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is from about 60,000 to about 120,000. In another embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is from about 70,000 to about 110,000. In another embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is from about 80,000 to about 100,000. The molecular weight distribution of each ethylene-α-olefin copolymer may be less than about 2.5, and more typically from about 2.1 to about 2.4. The polymer distribution of each ethylene-α-olefin copolymer measured by GPC is generally unimodal.

[0074] Other performance additives

[0075] 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 additive known to those skilled in the art can be used in the lubricating oil composition disclosed herein. Some suitable additives are described in RM Mortier et al., "Chemistry and Technology of Lubricants", 3rd edition, Springer (2010) and LR Rudnik, "Lubricant Additives: Chemistry and Applications", 2nd edition, CRC Press (2009).

[0076] Generally, when used, the concentration of each additive in the lubricating oil composition may be in the range of 0.001 to 10 wt % (e.g., 0.01 to 5 wt % or 0.05 to 2.5 wt %) of the lubricating oil composition. Including diluent oil, each additive in the lubricating oil composition may be in the range of 0.5 to 45 wt % (e.g., 1.0 to 45 wt %, 5.0 to 40 wt %, 10 to 35 wt %, 20 to 32 wt %, or 25 to 30 wt %) of the lubricating oil composition. In addition, the total amount of additives in the lubricating oil composition may be in the range of 0.001 to 20 wt % (e.g., 0.01 to 15 wt % or 0.1 to 10 wt %) of the lubricating oil composition. Including the diluent oil, the total amount of additives in the lubricating oil composition may range from 0.5 to 78 wt % (e.g., 1.0 to 78 wt %, 5.0 to 78 wt %, 10 to 78 wt %, 20 to 78 wt %, 30 to 78 wt % or 45 to 78 wt %) of the lubricating oil composition.

[0077] For 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 of these are discussed in more detail below.

[0078] Detergent

[0079] The lubricating oil composition of the present disclosure may contain one or more detergents. Detergents are additives that reduce the formation of piston deposits (e.g., high temperature varnish and paint deposits in engines). Detergents generally have acid neutralizing properties and are able to keep finely divided solids in suspension. Most detergents are metal salts of acidic organic compounds.

[0080] Metal-containing or ash-forming detergents can be used as both 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 includes a metal salt of an acidic organic compound.

[0081] In the art, detergents are often referred to as neutral or overbased detergents. Detergents containing substantially stoichiometric amounts of metal salts are often described as positive or neutral detergents. In embodiments where a large amount of a 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 an overbased detergent.

[0082] Overbased metal detergents are typically prepared by carbonating (with 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 hydroxide), and a promoter (such as xylene, methanol, and / or water). For example, to prepare overbased calcium sulfonate, calcium oxide or hydroxide reacts with gaseous carbon dioxide to form calcium carbonate during the carbonation process. The sulfonic acid is neutralized with excess CaO or Ca(OH)2 to form a sulfonate.

[0083] Overbased detergents can be further characterized as low overbased, moderately overbased, or highly overbased. Low overbased detergents can be, for example, overbased salts having a TBN of less than 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.

[0084] The moderately overbased detergent may be, for example, an overbased salt having a TBN of about 100 to about 250. In one embodiment, the moderately overbased salt may have a TBN of about 100 to about 200. In another embodiment, the moderately overbased salt may have a TBN of about 125 to about 175.

[0085] The overbased detergent may be, for example, an overbased salt having a TBN greater than 250. In one embodiment, the overbased salt may have a TBN of from about 250 to about 800.

[0086] Compounds useful in detergents include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates and naphthenates of metals, particularly alkali or alkaline earth metals such as barium, sodium, potassium, lithium, calcium and magnesium, and other oil-soluble carboxylates. The most commonly used metals are calcium and magnesium, and mixtures of calcium and / or magnesium with sodium, which may all be present in detergents used in lubricants.

[0087] In one embodiment, the detergent may be one or more alkali metal 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.

[0088] Suitable hydroxyaromatic compounds include phenol, catechol, resorcinol, hydroquinone, pyrogallol, cresol, etc. In certain embodiments, the preferred hydroxyaromatic compound is phenol.

[0089] The alkyl substituted portion of the alkali metal or alkaline earth metal salt of the alkyl substituted hydroxyaromatic carboxylic acid can be derived from an alpha-olefin having 10 to 80 carbon atoms. The olefin employed can be a linear, isomerized linear, branched or partially branched linear. The olefin can be a mixture of linear olefins, a mixture of isomerized linear olefins, a mixture of branched olefins, a mixture of partially branched linear olefins, or a mixture of any of the foregoing.

[0090] In some embodiments, the mixture of linear olefins is a mixture of normal alpha olefins selected from olefins having from 10 to 40 carbon atoms per molecule. In one embodiment, the normal alpha olefins are isomerized using at least one of a solid or liquid catalyst.

[0091] In some embodiments, at least about 75 mol % (e.g., at least about 80 mol %, at least about 85 mol %, at least about 90 mol %, at least about 95 mol %, or at least about 99 mol %) of the alkyl groups contained in the alkali metal or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid, such as the alkyl groups of the alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid detergent, are C 20 In some of these embodiments, the alkali metal or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid is an alkali metal or alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid derived from an alkyl-substituted hydroxybenzoic acid wherein the alkyl group is a C 20 To C 28 In another embodiment, at least about 50 mol % (e.g., at least 60 mol %, at least 70 mol %, at least 80 mol %, at least 85 mol %, at least 90 mol %, at least 95 mol % or at least 99 mol %) of the alkyl groups of the alkali metal or alkaline earth metal salt of alkyl-substituted hydroxybenzoic acid are C 20 To C 24 Alkyl substituents.

[0092] In another embodiment, at least about 50 mol% (e.g., at least 60 mol%, at least 70 mol%, at least 80 mol%, at least 85 mol%, at least 90 mol%, at least 95 mol%, or at least 99 mol%) of the alkyl groups of the alkali metal or alkaline earth metal salt of an alkyl-substituted hydroxybenzoic acid are C 14 To C 18 In another embodiment, the alkali metal or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid is derived from an alkyl group and an isomerized C 10 -C 40 Normal α-olefins, isomerized C 20 -C 28 Normal α-olefins or preferably isomerized C 20 -C 24 Normal alpha olefins. In one embodiment, the isomerized normal alpha olefin has an alpha olefin isomerization level between about 0.1 and about 0.4. In another embodiment, the alkyl group is derived from at least two alkyl phenols. The alkyl group on at least one of the at least two alkyl phenols is derived from an isomerized alpha olefin. The alkyl group on the second alkyl phenol may be derived from a branched or partially branched olefin, a highly isomerized olefin, or a mixture thereof.

[0093] The alkyl substituted portion of the alkali metal or alkaline earth metal salt of the alkyl substituted hydroxyaromatic carboxylic acid can be derived from cashew nut shell liquid (CNSL) or hydrogenated distilled CNSL. Distilled CNSL is a biodegradable mixture of meta-hydrocarbyl substituted phenols in which the hydrocarbyl groups are linear and unsaturated, including cardanol. Catalytic hydrogenation of distilled CNSL produces a mixture of meta-hydrocarbyl substituted phenols that is primarily rich in 3-pentadecylphenol.

[0094] The alkali metal or alkaline earth metal salt of the 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 1% to 99% of the ortho isomer and 99% to 1% of the para isomer. In another embodiment, the alkyl-substituted hydroxyaromatic carboxylic acid may contain about 5% to 70% of the ortho isomer and 95% to 30% of the para isomer.

[0095] The alkali metal salt or alkaline earth metal salt of an alkyl-substituted hydroxyaromatic carboxylic acid can be neutral or overbased. Typically, 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 an alkyl-substituted hydroxyaromatic carboxylic acid has been increased by methods such as the addition of an alkaline source (e.g., lime) and an acidic overbased compound (e.g., carbon dioxide).

[0096] As noted, certain embodiments of lubricating oil formulations may use one or more sulfonate detergents alone or in combination with other detergents. Sulfonates may be prepared from sulfonic acids, which may be obtained by sulfonation of alkyl-substituted aromatics (e.g., those obtained from petroleum fractionation) or by alkylation of aromatics. Examples of alkyl-substituted aromatic hydrocarbons that may be sulfonated include those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl or their halogen derivatives. Alkylation may be carried out in the presence of a catalyst using an alkylating agent having 3 to more than 70 carbon atoms. Alkaryl sulfonates typically contain 9 to 80 or more carbon atoms per alkyl-substituted aromatic moiety, preferably 16 to 60, preferably 16 to 30, and most preferably 20 to 24 carbon atoms.

[0097] The oil soluble sulfonates or alkylaryl sulfonic acids can be neutralized with metal oxides, hydroxides, alkoxides, carbonates, carboxylates, sulfides, hydrosulfides, nitrates, borates and ethers. The amount of metal compound is selected based on the desired TBN of the final product.

[0098] Metal salts of phenols and sulfurized phenols (e.g., phenates or sulfurized phenate detergents) are prepared by reaction of phenol or sulfurized phenol with a suitable metal compound such as an oxide or hydroxide. Sulfurized phenols can be prepared by reacting phenol with sulfur or a sulfur-containing compound such as hydrogen sulfide, sulfur monohalide or sulfur dihalide to form a product, which is generally a mixture of compounds in which two or more phenols are bridged by sulfur-containing bridges. Additional details on the general preparation of sulfurized phenates can be found, for example, in U.S. Pat. Nos. 2,680,096, 3,178,368 and 3,801,507, the contents of which are incorporated herein by reference.

[0099] The sulfur used to form the sulfurized compound may be in any allotropic form of sulfur.The sulfur may be present in the form of molten sulfur or a solid (eg, powder or granules) or a suspension of a solid in a compatible hydrocarbon liquid.

[0100] In some embodiments, it is desirable to use calcium hydroxide as the calcium base because it is more convenient to handle than, for example, calcium oxide, and also because it provides superior results. Other calcium bases may also be used, for example, calcium alkoxides.

[0101] Suitable alkylphenols that may be used are those in which the alkyl substituent contains a sufficient number of carbon atoms to render the resulting alkylphenol (e.g., overbased calcium sulphurized alkylphenate) composition oil soluble. Oil solubility may be provided by a single long chain alkyl substituent or by a combination of alkyl substituents. Typically, the alkylphenol used will be a mixture of different alkylphenols, e.g., C 20 To C 24Alkylphenols. In one embodiment, suitable alkylphenol compounds will be derived from isomerized normal alpha-olefin alkyl groups having from about 10 to about 40 carbon atoms per molecule, wherein the isomerization level of the alpha-olefin is from 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 alkylphenol compounds will be derived from an alkyl group that is a branched olefinic propylene oligomer or mixture thereof having from about 9 to about 80 carbon atoms. 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.

[0102] In one embodiment, suitable alkylphenol compounds include distilled cashew nut shell liquid (CNSL) or hydrogenated distilled CNSL. Distilled CNSL is a biodegradable mixture of meta-hydrocarbyl-substituted phenols, wherein the hydrocarbyl groups are linear and unsaturated, including cardanol. Catalytic hydrogenation of distilled CNSL produces a mixture of meta-hydrocarbyl-substituted phenols that is primarily rich in 3-pentadecylphenol.

[0103] The alkylphenol may be p-alkylphenol, m-alkylphenol or o-alkylphenol. In certain embodiments, such as where an overbased product is desired, the alkylphenol is preferably predominantly p-alkylphenol, with no more than about 45 mole % of the alkylphenol being o-alkylphenol; and more preferably, no more than about 35 mole % of the alkylphenol being o-alkylphenol. Alkyl-hydroxytoluene or xylene may 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 using distilled cashew nut shell liquid, catalytic hydrogenation of distilled CNSL may produce a mixture of meta-alkyl-substituted phenols.

[0104] Generally, the selection of alkylphenols can be based on the desired properties of the marine diesel engine lubricating oil composition, particularly TBN, and oil solubility. Additional information on the preparation of suitable alkylphenols can be found, for example, in U.S. Pat. Nos. 5,024,773, 5,320,763, 5,318,710 and 5,320,762, each of which is incorporated herein by reference.

[0105] Generally, the amount of detergent may 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 %, based on the total weight of the marine diesel engine lubricating oil composition.

[0106] The detergents may also include "hybrid" or "composite" detergents formed with mixed surfactant systems including phenate and / or sulfonate components, such as phenate / salicylate, sulfonate / phenate, sulfonate / salicylate, sulfonate / phenate / salicylate, as described, for example, in U.S. Patents 6,429,178, 6,429,179, 6,153,565. The detergents may also include methylene-bridged polyphenol compositions prepared by reacting phenol with formaldehyde or a reversible polymer thereof, optionally sulfiding the methylene-bridged intermediate, and subsequently reacting the intermediate with an excess of a 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.

[0107] Other detergents may be present in any suitable amount, such as from 0.1 to 45 wt %, or from 0.5 to 30 wt % of the lubricating oil composition.

[0108] Dispersants

[0109] The lubricating oil composition of the present disclosure may include one or more dispersants. During engine operation, oxidation byproducts that are insoluble in oil are produced. Dispersants help keep these byproducts in solution, thereby reducing their deposition on metal surfaces. Dispersants are generally referred to as ashless dispersants because they do not contain ash-forming metals before being mixed into the lubricating oil composition, and when added to the lubricant, they generally do not produce any ash. 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 which polyisobutylene substituents range from 500 Daltons to 5000 Daltons (e.g., 900 Daltons to 2500 Daltons). Succinimide dispersants and their preparation are disclosed, for example, in U.S. Patent Nos. 4,234,435 and 7,897,696. Succinimide dispersants are typically imides formed from polyamines, usually poly(ethylene amines).

[0110] 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 can be used alone or in combination with other dispersants.

[0111] The dispersant may also be post-treated by conventional methods by reaction with any of a variety of agents. These agents include boron compounds (eg, boric acid) and cyclic carbonates (ethylene carbonate).

[0112] Another class of dispersants includes Mannich bases. Mannich bases are materials formed by the condensation of higher molecular weight alkyl-substituted phenols, polyalkylene polyamines, and aldehydes such as formaldehyde. Mannich bases are described in more detail in U.S. Pat. No. 3,634,515.

[0113] Another class of dispersants includes high molecular weight esters 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. Pat. No. 3,381,022.

[0114] Another class of dispersants includes high molecular weight ester amides.

[0115] The dispersant may be present in an amount of 0.1 to 15 wt % of the lubricating oil composition.

[0116] Antiwear Agents

[0117] Antiwear agents reduce friction and excessive wear and are usually based on compounds containing sulfur or phosphorus or both. Of note are metal dihydrocarbyl dithiophosphates, where the metal can be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel, copper or zinc. Zinc dihydrocarbyl dithiophosphate (ZDDP) is an oil-soluble salt of a dihydrocarbyl dithiophosphate and can be represented by the formula:

[0118] Zn[SP(S)(OR)(OR')]2

[0119] wherein R and R' may be the same or different hydrocarbon groups containing from 1 to 18 (e.g., 2 to 12) carbon atoms. To achieve oil solubility, the total number of carbon atoms in the dithiophosphoric acid (i.e., R and R') will generally be 5 or greater.

[0120] Antiwear agents may be present in amounts of 0.1 to 6 wt % of the lubricating oil composition.

[0121] Antioxidants

[0122] Antioxidants slow down the oxidative degradation of the base oil during use. Such degradation can lead to deposits on metal surfaces, the presence of sludge, or an increase in the viscosity of the lubricant.

[0123] Useful antioxidants include hindered phenols. Hindered phenol antioxidants typically contain sec-butyl and / or tert-butyl groups as sterically hindered groups. The phenolic group may be further substituted with a hydrocarbyl group (typically a linear or branched alkyl group) and / or a bridging group connected 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-di-alkyl-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).

[0124] Sulfurized alkylphenols and their alkali metal and alkaline earth metal salts may also be used as antioxidants.

[0125] 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.

[0126] The antioxidant may be present in an amount of 0.01 to 15.0 wt % of the lubricating oil composition.

[0127] Friction modifiers

[0128] Friction modifiers are any materials that are capable of changing the coefficient of friction of a surface lubricated by any lubricant or fluid containing such materials. Suitable friction modifiers may 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, and condensation products of carboxylic acids and polyalkylene-polyamines. As used herein, the term "fat" associated with friction modifiers 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 friction modifier may be present in an amount of 0.01 to 10.0 wt % of the lubricating oil composition.

[0129] Rust inhibitor

[0130] Rust inhibitors generally protect the lubricated metal surface from chemical attack by water or other contaminants. Suitable rust inhibitors may include nonionic suitable rust inhibitors, including nonionic polyoxyethylene agents (e.g., polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octylstearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol 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 acid, partial esters thereof and nitrogen-containing derivatives thereof; and synthetic alkyl aryl sulfonates (e.g., metal dinonylnaphthalene sulfonates). Such additives may be present in an amount of 0.01 to 5% by weight of the lubricating oil composition.

[0131] Demulsifier

[0132] Demulsifiers can promote oil-water separation in lubricating oil compositions exposed to water or steam. Suitable demulsifiers include trialkyl phosphates, and various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures thereof. Such additives may be present in an amount of 0.01 to 5 weight percent of the lubricating oil composition.

[0133] Foam Inhibitor

[0134] Foam inhibitors retard the formation of stable foam. Silicones and organic polymers are typical foam inhibitors. For example, polysiloxanes, such as silicone oils or polydimethylsiloxanes, provide foam suppressing properties. Additional foam inhibitors include copolymers of ethyl acrylate and 2-ethylhexyl acrylate and optionally vinyl acetate. Such additives may be present in 0.001 to 1% by weight of the lubricating oil composition.

[0135] Viscosity Modifiers

[0136] Viscosity modifiers provide high and low temperature operability for lubricants. These additives impart shear stability at high temperatures and acceptable viscosity at low temperatures. Suitable viscosity modifiers may include polyolefins, olefin copolymers (OCPs), ethylene / propylene copolymers, polyisobutylenes, hydrogenated styrene-isoprene polymers, styrene / maleate copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkyl styrenes, and hydrogenated alkenyl aryl conjugated diene copolymers. Such additives may be present in 0.1 to 15 weight % of the lubricating oil composition.

[0137] Pour Point Depressants

[0138] Pour point depressants can reduce 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 paraffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkyl fumarates, vinyl esters of fatty acids, and allyl vinyl ethers. Such additives can be present in an amount of 0.01 to 1.0 weight percent of the lubricating oil composition.

[0139] Nonionic surfactants

[0140] Nonionic surfactants such as alkylphenols can improve asphaltene handling during engine operation. Examples of such materials include alkylphenols having alkyl substituents derived from straight or branched chain alkyl groups 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 may be present in the lubricating oil composition at 0.1 to 20 weight percent.

[0141] Markers

[0142] The lubricating oil composition of the present invention may contain a dye or marker component, such as a tracer, which is particularly useful for marking lubricants to protect brand assets, prevent misidentification, and help identify 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 or are currently used to mark or label lubricants include color and fluorescent dyes (e.g., diazo dyes, anthraquinone dyes, phthalein dyes, etc.), radioactive materials, metal compounds or complexes (e.g., metal organic compounds, metal salts, metal oxides, metal coordination complexes, etc.), and a variety of specific compounds that react with selected reagent combinations to provide derivatives of intense colors.

[0143] Examples of markers include materials selected from the group consisting of barium sulfate, bismuth trioxide, iodine, iodide, titanium oxide, zirconium oxide, gold, platinum, silver, tantalum, niobium, stainless steel, and combinations thereof. Materials provided in the form of 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, such as certain metal soaps, metal soaps of fatty acids, metal carboxylates, or known metal driers, may also be used as lubricant markers. Examples of zirconium-containing materials may include zirconium carboxylates, such as zirconium 2-ethylhexanoate, zirconium octoate, and zirconium salicylate materials.

[0144] Use of lubricating oil composition

[0145] The lubricant composition can be effectively used as a cylinder lubricating oil for compression ignition internal combustion engines (including marine diesel engines, stationary gas engines, etc.).

[0146] The internal combustion engine can be a 2-stroke engine. In one embodiment, the internal combustion engine is a marine diesel engine. In certain embodiments, the marine diesel engine can be a low-speed crosshead 2-stroke compression ignition engine with a speed of 200 rpm or lower (e.g., 60 rpm to 200 rpm).

[0147] Marine diesel engines may be lubricated with a marine diesel cylinder lubricant (eg, typically in 2-stroke engines).

[0148] The term "marine" does not limit engines to those used in watercraft; as understood in the art, it also includes those used in other industrial applications, such as auxiliary power generation for main propulsion and stationary land-based engines for power generation.

[0149] In some embodiments, the internal combustion engine may use residual fuel, marine residual fuel, low sulfur marine residual fuel, marine distillate fuel, low sulfur marine distillate fuel, or high sulfur fuel.

[0150] Internal combustion engines may also be run on "gaseous fuels," such as methane-based fuels (eg, natural gas), biogas, vaporized liquefied gas, or vaporized liquefied natural gas (LNG).

[0151] Example

[0152] The following exemplary embodiments are intended to be non-limiting and demonstrate the effect of using a suitable olefin copolymer thickener in combination with a light neutral base oil or a heavy neutral base oil to achieve various viscosity levels.

[0153] The following components were used in the formulation of the marine lubricating oil compositions of the Examples. Generally speaking, the marine lubricating oil compositions of the Examples comprise an oil of lubricating viscosity (base oil component), a thickener, and an additive package.

[0154] The base oil components used in the formulations of the examples include:

[0155] XOM 150N: ExxonMobil 150N Class I lubricant, kv@100℃5.1mm 2 / s

[0156] XOM 600N: ExxonMobil 600N: Class I lubricant, kv@100℃12.4mm 2 / s

[0157] XOM 2500BS: ExxonMobil 2500BS: Class I bright oil lubricant, kv@100℃30.6mm 2 / s

[0158] RLOP 600R: Chevron 600R RLOP: Class II lubricant, kv@100℃12.0mm 2 / s

[0159] RLOP 220R: Chevron 220RLOP: Class II lubricant, kv@100℃6.4mm 2 / s

[0160] The olefin copolymer thickener used in the formulation of the examples is a concentrate of an olefin copolymer, particularly an ethylene-propylene copolymer, in a diluent. Therefore, in the table listed below, the weight percentages of the OCP thickeners listed are calculated as such, not on an active basis. To obtain the weight percentage of the olefin copolymer based on active substance, the weight percentage of the OCP thickener listed should be multiplied by the weight percentage of the olefin copolymer present in the OCP thickener.

[0161] OCP-1: A concentrate having 6.30 wt% of a 50 SSI olefin copolymer in a Group II diluent oil and containing 60% ethylene and having a number average molecular weight (Mn) of 112,000 g / mol.

[0162] The additive package used in the example formulations included:

[0163] Additive Package A: 6.92 wt% 420BN calcium sulfonate detergent oil concentrate (38.7 wt% diluent oil), 6.0 wt% 17BN calcium sulfonate detergent oil concentrate (50.0 wt% diluent oil), 9.0 wt% derived from C 20 To C 24 An oil concentrate of 95BN calcium sulfide phenate detergent of isomerized alpha olefins (20 wt% diluent oil), 0.2 wt% of an oil concentrate of a bis-succinimide dispersant derived from a 1000 MW PIB (32 wt% diluent oil), 1.5 wt% antioxidant, 0.11 wt% foam inhibitor and diluent oil.

[0164] Additive Package B: 5.0 wt% of 20 To C 24 Oil concentrate of 260BN calcium sulfide phenate detergent of isomerized alpha olefins (40 wt% diluent oil), 4.0 wt% derived from C 20 To C 24Oil concentrate of 410BN overbased calcium carboxylate detergent of isomerized alpha olefins (33.0 wt.% diluent oil), 5.45 wt.% derived from C 20 To C 24 An oil concentrate of 180BN overbased calcium carboxylate detergent of isomerized normal alpha olefins (20 wt% diluent oil), 0.2 wt% of an oil concentrate of a bis-succinimide dispersant derived from a 1000 MW PIB (32 wt% diluent oil), 1.5 wt% antioxidant, 0.11 wt% foam inhibitor and diluent oil.

[0165] Additive Package C: 1.03 wt% 420BN calcium sulfonate detergent oil concentrate (38.7 wt% diluent oil), 6.0 wt% 17BN calcium sulfonate detergent oil concentrate (50.0 wt% diluent oil), 9.0 wt% derived from C 20 To C 24 An oil concentrate of 95BN calcium sulfide phenate detergent of isomerized alpha olefins (20 wt% diluent oil), 0.2 wt% of an oil concentrate of a bis-succinimide dispersant derived from a 1000 MW PIB (32 wt% diluent oil), 1.5 wt% antioxidant and 0.11 wt% foam inhibitor.

[0166] Additive Package D: 3.0 wt% of 20 To C 24 Oil concentrate of 260BN calcium sulfide phenate detergent of isomerized alpha olefins (40 wt% diluent oil), 0.3 wt% derived from C 20 To C 24 Oil concentrate of 410BN overbased calcium carboxylate detergent of isomerized alpha olefins (33.0 wt. % diluent oil), 2.9 wt. % derived from C 20 To C 24 An oil concentrate of 180BN overbased calcium carboxylate detergent of isomerized normal alpha olefins (20 wt% diluent oil), 0.2 wt% of an oil concentrate of a bis-succinimide dispersant derived from 1000 MWPIB (32 wt% diluent oil), 1.5 wt% antioxidant and 0.11 wt% foam inhibitor.

[0167] The following examples were evaluated for their degree of oxidative stability using the following test. The results for each example are listed in Tables 2-5.

[0168] Test Method

[0169] DSC oxidation test

[0170] The DSC test is used to evaluate the thin film oxidation stability of the test oil according to ASTM D-6186. During the test, the heat flow into and out of the test oil in the sample cup is compared to the reference cup. The oxidation onset temperature is the temperature at which the test oil begins to oxidize. The oxidation induction time is the time at which the test oil begins to oxidize. Longer oxidation induction times mean better performance. The oxidation reaction is exothermic and is clearly shown by the heat flow. The oxidation induction time is calculated to evaluate the thin film oxidation stability of the test oil.

[0171] Modified Institute of Petroleum 48 (MIP-48) test

[0172] The MIP-48 test consists of a hot part and an oxidation part. During both parts of the test, the test samples are heated. In the hot part of the test, nitrogen is passed through the heated oil sample for 24 hours, and at the same time, during the oxidation part of the test, air is passed through the heated oil sample for 24 hours. The samples are cooled and the viscosity of the two samples is measured. The viscosity increase of the test oil caused by oxidation is measured and corrected for thermal effects. The oxidation-based viscosity increase of each marine lubricant composition is calculated by subtracting the kinematic viscosity of the nitrogen-blown sample at 200°C from the kinematic viscosity of the air-blown sample at 200°C, and dividing the subtraction by the kinematic viscosity of the nitrogen-blown sample at 200°C. This is done to correct for potential evaporation effects or any other thermal effects during the test, thereby focusing on the impact of oxidation. This correction may result in negative values. Test oils that show better stability to oxidation-based viscosity increase will result in lower % absolute values.

[0173] result

[0174] Example 1 and Comparative Example A

[0175] Example 1 and Comparative Example A were formulated to 40BN, SAE 50 viscosity grade (kv@100°C was 18.5 mm 2 / s) marine cylinder lubricant composition. The finished oil lubricant of Comparative Example A was formulated using a large amount of heavy neutral oil Chevron RLOP600R Group II base oil and a small amount of XOM Core 2500BS to obtain a suitable lubricant viscosity. The finished oil lubricant of Example 1 contains a combination of light neutral oil Chevron220R Group II base oil and an olefin copolymer thickener to obtain a suitable lubricant viscosity. The oxidation stability of each lubricant was evaluated using a DSC oxidation test. The results of each example are listed in Table 2 below. The weight percentages of the listed OCP thickeners are calculated as is.

[0176] Table 2

[0177]

[0178] The results listed in Table 2 show that the marine cylinder lubricant composition containing the combination of light neutral oil 220R and olefin copolymer thickener exhibits surprisingly better oxidation performance than Comparative Example A, as evidenced by the higher oxidation induction time of the inventive example compared to the comparative example. Therefore, in certain embodiments, a marine cylinder lubricant formulation comprising a combination of light neutral oil and olefin copolymer thickener can have enhanced performance compared to a marine cylinder lubricant formulation without olefin copolymer thickener.

[0179] Example 2 and Comparative Example B

[0180] Example 2 and Comparative Example B were formulated to 40BN, SAE 50 viscosity grade (kv@100°C was 18.5 mm 2 / s) marine cylinder lubricant composition. The finished oil lubricant of Comparative Example B was formulated using a large amount of heavy neutral oil Chevron RLOP600R Group II base oil and a small amount of XOM Core 2500BS to obtain a suitable lubricant viscosity. The finished oil lubricant of Example 2 contains a combination of light neutral oil Chevron220R Group II base oil and an olefin copolymer thickener to obtain a suitable lubricant viscosity. The DSC oxidation test was used to evaluate the oxidation stability of each lubricant. The results for each sample are listed in Table 3 below. The weight percentages of the listed OCP thickeners are calculated as is.

[0181] Table 3

[0182]

[0183] The results listed in Table 3 show that the marine cylinder lubricant composition containing the combination of light neutral oil 220R and olefin copolymer thickener exhibits surprisingly better oxidation performance than Comparative Example B, as evidenced by the higher oxidation induction time of the inventive examples compared to the comparative examples. Thus, in certain embodiments, a marine cylinder lubricant formulation comprising a combination of light neutral oil and olefin copolymer thickener may have enhanced performance compared to a marine cylinder lubricant formulation without the olefin copolymer thickener.

[0184] Example 3 and Comparative Example C

[0185] Example 3 and Comparative Example C were formulated to 15BN, SAE 50 viscosity grade (kv@100°C was 18.5 mm 2 / s) marine cylinder lubricant composition. The finished oil lubricant of Comparative Example C was formulated using a large amount of heavy neutral oil Chevron RLOP600R Group II base oil and a small amount of XOM Core 2500BS to obtain a suitable lubricant viscosity. The finished oil lubricant of Example 3 contains a combination of light neutral oil Chevron220R Group II base oil and an olefin copolymer thickener to obtain a suitable lubricant viscosity. The DSC oxidation test was used to evaluate the oxidation stability of each lubricant. The results for each sample are listed in Table 4 below. The weight percentages of the listed OCP thickeners are calculated as is.

[0186] Table 4

[0187]

[0188] The results listed in Table 4 show that the marine cylinder lubricant composition containing the combination of light neutral oil 220R and olefin copolymer thickener exhibits surprisingly better oxidation performance than Comparative Example C, as evidenced by the higher oxidation induction time of the inventive examples compared to the comparative examples. Thus, in certain embodiments, a marine cylinder lubricant formulation comprising a combination of light neutral oil and olefin copolymer thickener may have enhanced performance compared to a marine cylinder lubricant formulation without the olefin copolymer thickener.

[0189] Example 4 and Comparative Example D

[0190] Example 4 and Comparative Example D were formulated to 15BN, SAE 50 viscosity grade (kv@100°C was 18.5 mm 2 / s) marine cylinder lubricant composition. The finished oil lubricant of Comparative Example D was formulated using a large amount of heavy neutral oil Chevron RLOP600R Group II base oil and a small amount of XOM Core 2500BS to obtain a suitable lubricant viscosity. The finished oil lubricant of Example 4 contains a combination of light neutral oil Chevron 220R Group II base oil and an olefin copolymer thickener to obtain a suitable lubricant viscosity. The oxidation stability of each lubricant was evaluated using a DSC oxidation test. The results for each sample are listed in Table 5 below.

[0191] Table 5

[0192]

[0193] The results listed in Table 5 show that the marine cylinder lubricant composition containing the combination of light neutral oil 220R and an olefin copolymer thickener exhibits surprisingly better oxidation performance than Comparative Example D, as evidenced by the higher oxidation induction time of the inventive examples compared to the comparative examples. Thus, in certain embodiments, a marine cylinder lubricant formulation comprising a combination of a light neutral oil and an olefin copolymer thickener may have enhanced performance compared to a marine cylinder lubricant formulation without an olefin copolymer thickener.

[0194] The above specific embodiments have been shown by way of example, and it should be understood that these embodiments are susceptible to various modifications and alternative forms, and can also be used in any appropriate combination. It should also be understood that the claims are not intended to be limited to the specific forms disclosed, but to cover all modifications, equivalent forms, and alternative forms that fall within the spirit and scope of the present disclosure.

Claims

1. A marine diesel engine cylinder lubricating oil composition, comprising: (a) a major amount of oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000; and The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine diesel engine lubricating oil composition is a monograde lubricating oil composition that complies with the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricating oils as revised in January 2015.

2. The composition of claim 1, wherein the one or more olefin copolymers are bimodal and have a content of ethylene units ranging from 30% to 80% by weight relative to the weight of the olefin copolymer.

3. The composition of claim 1, wherein the one or more olefin copolymers are present in an amount of 0.5 to 5 weight percent of the lubricating oil composition on an active matter basis.

4. The composition of claim 1, wherein the one or more olefin copolymers are present in an amount of 1 to 2 weight percent of the lubricating oil composition on an active matter basis.

5. The composition of claim 1 wherein the one or more olefin copolymers are the only viscosity modifiers present in the lubricating oil composition.

6. The composition of claim 1, wherein the lubricating oil composition is free of bright stock.

7. The composition of claim 1, wherein the lubricating oil composition has a sulfated ash content of 1.5 wt% or more.

8. The composition of claim 1, wherein the lubricating oil composition has a TBN of 15 to 40 mg KOH / g.

9. The composition of claim 1, wherein the one or more olefin copolymers consist of one or more ethylene propylene copolymers.

10. The composition of claims 1 to 9, wherein the oil of lubricating viscosity has a kinematic viscosity of 4.0 mm at 100°C. 2 / s to less than 8.5mm 2 / s.

11. A composition as claimed in claims 1 to 9, wherein the oil of lubricating viscosity has a kinematic viscosity of 8.5 mm at 100°C. 2 / s to 15.0mm 2 / s.

12. A method of thickening a cylinder lubricating oil composition in a marine diesel internal combustion engine, the method comprising adding to the engine a cylinder lubricating oil composition comprising: (a) a major amount of oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000; and The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine diesel engine lubricating oil composition is a monograde lubricating oil composition that complies with the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricating oils as revised in January 2015.

13. The method of claim 12, wherein the one or more olefin copolymers are present in an amount of 1 to 2 weight percent of the lubricating oil composition on an active matter basis.

14. The method of claim 12, wherein the one or more olefin copolymers are the only viscosity modifiers present in the lubricating oil composition.

15. The method of claim 12, wherein the lubricating oil composition is free of bright stock.

16. The method of claim 12, wherein the lubricating oil composition has a sulfated ash content of 1.5 wt% or more.

17. The method of claim 12, wherein the lubricating oil composition has a TBN of 15 to 40 mg KOH / g.

18. The method of claim 12, wherein the one or more olefin copolymers consist of one or more ethylene propylene copolymers.

19. The method of claims 13 to 18, wherein the oil of lubricating viscosity has a kinematic viscosity of 4.0 mm at 100°C. 2 / s to less than 8.5mm 2 / s.

20. The method of claims 13 to 18, wherein the oil of lubricating viscosity has a kinematic viscosity of 8.5 mm at 100°C. 2 / s to 15.0mm 2 / s.

21. A method of controlling deposit formation in an internal combustion engine, the method comprising operating the internal combustion engine with a cylinder lubricating oil composition comprising: (a) a major amount of oil of lubricating viscosity; and (b) one or more olefin copolymers having a number average molecular weight of 30,000 to 120,000; and The marine diesel engine lubricating oil composition has a TBN of less than 70 mg KOH / g, and further wherein the marine diesel engine lubricating oil composition is a monograde lubricating oil composition that complies with the SAE J300 specification requirements for SAE 40, SAE 50 or SAE 60 monograde lubricating oils as revised in January 2015.

22. The method of claim 21, wherein the one or more olefin copolymers are present in an amount of 1 to 2 weight percent of the lubricating oil composition on an active matter basis.

23. The method of claim 21, wherein the one or more olefin copolymers are the only viscosity modifiers present in the lubricating oil composition.

24. The method of claim 21, wherein the lubricating oil composition is free of bright stock.

25. The method of claim 21, wherein the lubricating oil composition has a sulfated ash content of 1.5 wt% or more.

26. The method of claim 21, wherein the lubricating oil composition has a TBN of 15 to less than 40 mg KOH / g.

27. The method of claim 21, wherein the one or more olefin copolymers consist of one or more ethylene propylene copolymers.

28. The method of claims 21 to 27, wherein the oil of lubricating viscosity has a kinematic viscosity of 4.0 mm at 100°C. 2 / s to less than 8.5mm 2 / s.

29. The method of claims 21 to 27, wherein the oil of lubricating viscosity has a kinematic viscosity of 8.5 mm at 100°C. 2 / s to 15.0mm 2 / s.

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