Lubricant composition with improved economic fuel performance in hybrid vehicles

Abstract

The present invention relates to a lubricant composition comprising at least one diester of formula Ra-C (O)-O-([C (R) 2] n-O) s-C (O)-Rb, and at least one Group II + base oil having a kinematic viscosity of less than 12 cSt, measured at 40 DEG C according to ASTM D445, a kinematic viscosity of less than 3 cSt, measured at 100 DEG C according to ASTM D445, and a sulfur content of less than or equal to 5 ppm. The invention also relates to the use of said lubricant composition for lubricating components of a motor vehicle engine.

Description

Technical Field

[0001] The subject of the invention is a lubricant composition for light vehicles, in particular hybrid vehicles, and more particularly for plug-in hybrid vehicles and hybrid vehicles including a range extender. Another subject of the invention is to improve the low temperature fuel economy of the engine of such a vehicle. Background Art

[0002] A hybrid vehicle consists of two engines, an internal combustion engine and an electric motor. In most hybrid vehicles, the internal combustion engine drives the wheels and is assisted by the electric motor. The battery provides the power required to run the electric motor. In the case of conventional hybrid vehicles, the battery is recharged during braking and deceleration by a kinetic energy recovery system (KERS) integrated into the vehicle.

[0003] There are different hybrid vehicle technologies. Hybrid technologies include:

[0004] - Micro-hybrid vehicles (also called mild hybrids), these vehicles are equipped with a "stop & start" system that recovers the energy generated by braking to charge a battery that can temporarily assist the engine:

[0005] - Mild hybrid vehicles, including electric assistance during acceleration; and

[0006] - A full hybrid vehicle is a vehicle with full hybrid power. At low speeds, when the battery is charged, the electric motor is responsible for starting and propulsion. At high speeds, or when the battery is discharged, the internal combustion engine takes over, and when increased power is needed (for example, for acceleration), both engines work together. Thus, it is possible to travel several kilometers with the internal combustion engine switched off.

[0007] Other complementary technologies have been developed recently: plug-in hybrid vehicles and hybrid vehicles with range extenders. A plug-in hybrid vehicle (also called plug-in hybrid) comprises an internal combustion engine and an electric motor; the battery can be recharged from the electricity mains, whereby such a vehicle can travel a distance of several tens of kilometers, for example 50 kilometers, in 100% electric mode. In a hybrid vehicle including a range extender, only the electric motor drives the wheels. The electric motor is powered by the battery for several tens of kilometers. When the battery reaches a certain charge threshold (for example, about 30%), the engine starts and drives the current generator to produce the power required to recharge the battery and maintain the operation of the electric motor.

[0008] In both types of hybrid vehicles, the internal combustion engine is used less frequently and therefore runs at lower temperatures (around or even below 40°C) than the engines of other types of hybrid vehicles. However, at low temperatures, conventional lubricant compositions are more viscous and the additives are not as active as in conventional applications at higher temperatures. Current lubricants have been optimized to save fuel consumption in hot conditions.

[0009] The demand for high-performance lubricant compositions is increasing, in particular with regard to energy efficiency and more specifically improving the fuel economy (Fuel Economy) or simply fuel Eco (FE) of lubricant compositions or reducing the fuel consumption of engines, more specifically engines of hybrid vehicles.

[0010] The goal of improving FE is in particular to have a lubricant composition that is as fluid as possible and therefore has a low viscosity that can be associated with a low grade. Summary of the invention

[0011] Therefore, an object of the present invention is to provide a lubricant composition for lubricating an engine of a plug-in hybrid vehicle or a hybrid vehicle including a range extender, which has improved fuel economy performance.

[0012] Another object of the present invention is to provide a lubricant composition for use in an engine of a light-duty vehicle, particularly a hybrid vehicle, that exhibits improved fuel economy performance at low temperatures.

[0013] Therefore, the present invention relates to a lubricant composition comprising:

[0014] - at least one diester of formula (I):

[0015] R a -C(O)-O-([C(R)2] n -O) s -C(O)-R b (I)

[0016] in:

[0017] .R groups independently of one another represent a hydrogen atom or a straight-chain or branched alkyl group containing 1 to 5 carbon atoms, in particular a methyl group, an ethyl group or a propyl group, preferably a methyl group;

[0018] .s means 1 or 2;

[0019] .n represents 1, 2, or 3, provided that when s is different from 1, n may be the same or different:

[0020] .R a and R bmay be identical or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms;

[0021] Provided that, when s is equal to 2 and ns is likewise equal to 2, at least one R group represents a straight or branched chain alkyl group having 1 to 5 carbon atoms; and

[0022] Provided that, when s is equal to 1 and n is equal to 3, at least one R group bonded to the carbon in the beta position to the oxygen atom of the ester functional group represents a hydrogen atom, and

[0023] - At least one Group II+ base oil having a kinematic viscosity of less than 12 cSt measured at 40°C according to ASTM D445, a kinematic viscosity of less than 3 cSt measured at 100°C according to ASTM D445 and a sulfur content less than or equal to 5 ppm.

[0024] The lubricant composition according to the invention is therefore based on a combination of at least one specific Group II+ base oil and at least one diester of formula (I) as defined above.

[0025] Surprisingly, it has been discovered that despite the incompatibilities associated with the use of esters, especially in the presence of molybdenum-based friction modifiers, such compositions have improved fuel economy performance.

[0026] Diesters having formula (I)

[0027] According to one embodiment, the diester of the invention corresponds to formula (I) defined above, wherein, when s is not equal to 1, all n are identical.

[0028] Preferably, in the diesters of formula (I) according to the invention, n represents 2 or 3, preferably 2.

[0029] Preferably, in formula (I), at least one group R represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably 1 to 4 carbon atoms, more preferably methyl, ethyl or propyl, advantageously methyl.

[0030] According to a specific embodiment, the diester of formula (I) according to the invention is a diester having the following formula (I'):

[0031] R a -C(O)-O-([C(R)2] n -O)-([C(R')2] m -O) s-1 -C(O)-R b (I')

[0032] in:

[0033] .R and R' independently represent a hydrogen atom or a straight or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl group, an ethyl group or a propyl group, preferably a methyl group;

[0034] .s means 1 or 2;

[0035] .n means 2;

[0036] .m means 2;

[0037] .R a and R b may be identical or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms;

[0038] Provided that, when s is equal to 2, at least one of the radicals R and R' represents a straight-chain or branched alkyl radical containing 1 to 5 carbon atoms.

[0039] Advantageously, at least one of the radicals R or R' in the diester of formula (I') represents a linear or branched alkyl radical containing 1 to 5 carbon atoms, preferably 1 to 4 carbon atoms, preferably methyl, ethyl or propyl, advantageously methyl.

[0040] Preferably, in the compounds of formula (I) and (I'), R a and R b A straight chain having 7 to 14 carbon atoms, preferably 8 to 12 carbon atoms.

[0041] In one specific embodiment, in formula (I) or (I'), s represents 2.

[0042] The diester of the present invention is preferably a compound of formula (I'a):

[0043] R a -C(O)-O-([C(R)2] n -O)-([C(R')2] m -O)-C(O)-R b (I'a)

[0044] in:

[0045] .R and R' independently represent a hydrogen atom or a straight or branched alkyl group having 1 to 5 carbon atoms, preferably a methyl group, an ethyl group or a propyl group, preferably a methyl group;

[0046] .n means 2;

[0047] .m means 2;

[0048] .R a and R bmay be identical or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms;

[0049] Provided that at least one of the radicals R or R' represents a straight-chain or branched alkyl radical having 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl.

[0050] Preferably, at least one R group represents a straight or branched alkyl group containing 1-5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl; and at least one R' represents a straight or branched alkyl group containing 1-5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl.

[0051] Even more preferably, in formula (I'a), one of the groups R represents a straight-chain or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl, ethyl or propyl group, preferably a methyl group; and one of the groups R' represents a straight-chain or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl, ethyl or propyl group, preferably a methyl group; and the other groups R and R' represent a hydrogen atom.

[0052] In one embodiment, the diester of the present invention is a compound of formula (I"a):

[0053] R a -C(O)-O-CHR 1 -CHR 2 -O-CHR 3 -CHR 4 -OC(O)-R b (I”a)

[0054] in:

[0055] .Group R 1 and R 2 One of them represents a straight or branched alkyl group having 1 to 5 carbon atoms, and the other represents a hydrogen atom;

[0056] .Group R 3 and R 4 One of them represents a straight or branched alkyl group having 1 to 5 carbon atoms, and the other represents a hydrogen atom;

[0057] .R a and R b The same or different, as defined above.

[0058] Preferably, in formula (I"a):

[0059] .Group R 1 and R 2 One represents a methyl group, an ethyl group or a propyl group, preferably a methyl group, and the other represents a hydrogen atom;

[0060] .Group R 3 and R 4 One of them represents a methyl group, an ethyl group or a propyl group, preferably a methyl group, and the other represents a hydrogen atom.

[0061] According to another embodiment, in formula (I) or (I'), s represents 1 and the diester of the invention has formula (I'b):

[0062] R a -C(O)-O-([C(R)2] n -O)-C(O)-R b (I'b)

[0063] in:

[0064] R and R independently represent a hydrogen atom or a straight-chain or branched alkyl group having 1 to 5 carbon atoms, preferably a methyl group, an ethyl group or a propyl group, preferably a methyl group;

[0065] .n means 2;

[0066] .R a and R b may be identical or different and independently of one another represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms.

[0067] Preferably, in formula (I'b), at least one group R represents a straight-chain or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl, ethyl or propyl group, preferably a methyl group.

[0068] Preferably, in formula (I'b), one of the radicals R represents a straight-chain or branched alkyl radical containing 1 to 5 carbon atoms, preferably a methyl radical, an ethyl radical or a propyl radical, preferably a methyl radical, and the other radical represents a hydrogen atom.

[0069] Within the framework of the present invention, it is to be understood that the expression "comprising xy carbon atoms" also encompasses the boundaries x and y.

[0070] Within the framework of the present invention, the term "linear chain of xy carbon atoms" is to be understood as a saturated or unsaturated, preferably saturated, carbon chain comprising xy carbon atoms one after another, carbon atoms possibly present at the level of branching of the carbon chain not being counted in the number of carbon atoms (xy) forming the linear chain.

[0071] According to a specific embodiment, in formula (I), (I'), (I'a), (I"a) or (I'b), R a and R b Same or different, of vegetable, animal or petroleum origin.

[0072] According to a specific embodiment, in formula (I), (I'), (I'a), (I"a) or (I'b), R a and R b Can be the same or different, indicating the saturated portion.

[0073] According to a specific embodiment, in formula (I), (I'), (I'a), (I"a) or (I'b), R a and R b are the same or different, indicating a linear moiety. More specifically, R a and R b Identical or different, it refers to a saturated straight-chain hydrocarbon moiety containing 6 to 18 carbon atoms, preferably 7 to 17 carbon atoms, especially 7 to 14 carbon atoms, preferably 8 to 12 carbon atoms, especially 9 or 12 carbon atoms.

[0074] According to another preferred embodiment, in formula (I), (I'), (I"a), (I'a) or (I'b), R a and R b The same or different, denotes a saturated straight-chain alkyl group containing 6 to 18 carbon atoms, preferably 7 to 17 carbon atoms, in particular 7 to 14 carbon atoms, preferably 8 to 12 carbon atoms, in particular 9 or 12 carbon atoms.

[0075] Preferably, R a and R b same.

[0076] The diesters of formula (I) may be commercially available or prepared according to synthesis methods described in the literature and known to those skilled in the art, in particular according to the method described in WO 2019 / 025446.

[0077] According to one embodiment, the lubricant composition according to the invention comprises 15% to 90% by weight, preferably 25% to 85% by weight, in particular 40% to 80% by weight of diester of formula (I), relative to the total weight of the lubricant composition.

[0078] Group II + base oil

[0079] According to one embodiment, the above-mentioned Group II+ base oil has an aromatics content less than or equal to 2% by weight, relative to the total weight of the base oil, and preferably zero.

[0080] Preferably, the abovementioned Group II+ base oils have a content of paraffinic compounds less than or equal to 85% by weight, preferably less than or equal to 80% by weight, relative to the total weight of the base oil.

[0081] Preferably, the abovementioned Group II+ base oils have a naphthenic compound content less than or equal to 30% by weight, preferably less than or equal to 25% by weight, relative to the total weight of the base oil.

[0082] The KV40 and KV100 of the above base oils were measured according to standard ASTM D445.

[0083] As described above, the KV40 (kinematic viscosity measured at 40° C.) of the above base oil is less than or equal to 12 cSt.

[0084] As described above, the KV100 (kinematic viscosity measured at 100° C.) of the above base oil is less than or equal to 3 cSt.

[0085] Preferably, the sulfur content of the above base oil is 0.00001 ppm-5 ppm, preferably 0.0001 ppm-1 ppm.

[0086] This content is measured according to standard ASTM D2622.

[0087] According to one embodiment, the lubricant composition according to the invention comprises 5% to 60% by weight, preferably 8% to 40% by weight, in particular 10% to 30% by weight, of a Group II+ base oil as defined above, relative to the total weight of the lubricant composition.

[0088] Preferably, the lubricant composition according to the invention has a grade according to the SAE J300 classification of type XW-(Y), wherein X represents 0, 5 or 10 and Y represents an integer from 6 to 50, preferably 8 or 40, preferably X=0 and Y=8.

[0089] The Noack volatility at 250° C. is measured according to method CEC L-40-A-93. Preferably, the lubricant composition of the present invention has a Noack volatility at 250° C. of 10% to 20%, and preferably of 12% to 15%.

[0090] The lubricant composition according to the present invention may further comprise compounds or additives in addition to the above-mentioned Group II+ base oil and the diester of formula (I).

[0091] According to a particular embodiment, the lubricant composition of the invention comprises an additional base oil different from the Group II+ base oil defined above.

[0092] The additional base oil used in the lubricant composition of the invention may be chosen among oils of mineral or synthetic origin belonging to group IV according to the category defined by the API classification (or its equivalent according to the ATIEL classification) (Table 1) or mixtures thereof.

[0093] [Table 1]

[0094]

[0095] Mineral base oils include any type of base oil obtained by atmospheric and vacuum distillation of crude oil followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0096] It is further possible to use mixtures of synthetic oils and mineral oils.

[0097] The additional base oil of the lubricant composition according to the invention may further be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins. The polyalphaolefins used as base oils are obtained, for example, from monomers containing 4 to 32 carbon atoms, such as octene or decene, and have a viscosity at 100° C. of 1.5 to 15 mm according to standard ASTM D445. 2 .s -1 According to standard ASTM D5296, its average molar mass is usually between 250 and 3,000.

[0098] The composition of the present invention may further comprise at least one additive.

[0099] A variety of additives may be used in the lubricating compositions according to the present invention.

[0100] According to one embodiment, the lubricant composition according to the invention also comprises a friction modifier additive, preferably containing molybdenum.

[0101] Preferably, the lubricant composition according to the present invention comprises at least one friction modifier additive. The friction modifier additive is used to limit friction by forming an adsorbed monolayer on the metal surface in contact with it. It can be selected from compounds providing metal elements and ashless compounds. Compounds providing metal elements include transition metal complexes, such as Mo and Sb, Sn, Fe, Cu, Zn, whose ligands can be hydrocarbon compounds containing oxygen, nitrogen, sulfur or phosphorus atoms. Ashless friction modifier additives are generally of organic origin and can be selected from fatty acids and polyol esters, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty epoxide borates, amino acids or fatty acid glycerides different from the monoesters required by the present invention. According to the present invention, the fatty compound contains at least one hydrocarbon part containing 10-24 carbon atoms. More specifically, the molybdenum compound can be selected from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP) and mixtures thereof. Advantageously, the lubricant composition according to the invention may comprise 0.01-10 wt. % or 0.01-5 wt. %, preferably 0.01-2 wt. %, preferably 0.1-1.5 wt. % or 0.1-2 wt. % of friction modifier additive relative to the total weight of the lubricant composition.

[0102] The molybdenum (Mo) in the lubricant composition of the present invention is derived from an organic molybdenum compound, in particular a compound selected from molybdenum dithiocarbamate derivatives (MoDTC), molybdenum dithiophosphate derivatives (MoDTP) or sulfur-free molybdenum complexes, preferably molybdenum dithiocarbamate derivatives (MoDTC).

[0103] Molybdenum dithiocarbamate compounds (MoDTC compounds) are complexes formed by bonding a metal core to one or more ligands independently selected from alkyl dithiocarbamate moieties. The MoDTC compounds of the composition used according to the invention may contain 0.01-5 wt. %, preferably 0.1-1.5 wt. % of molybdenum, relative to the total mass of the MoDTC compounds.

[0104] Preferably, the composition according to the invention comprises a friction modifier additive comprising molybdenum and preferably comprises (in active content) 1 to 1,000 ppm, preferably 400 to 600 ppm, of Mo relative to the weight of the lubricant composition.

[0105] According to one embodiment, the lubricant composition may further comprise at least one viscosity index (VI) improver additive. Viscosity index improvers, more specifically viscosity index improving polymers, provide good cold resistance and minimal viscosity at high temperatures. Examples of viscosity index improving polymers include polymer esters, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, homopolymers or copolymers of olefins (e.g., ethylene or propylene), polyacrylates and polymethacrylates (PMA), preferably homopolymers, polymethacrylates or copolymers of olefins (e.g., ethylene or propylene).

[0106] More specifically, the lubricant composition according to the invention may comprise 1% to 15% by weight, preferably 5% to 10% by weight, of an additive for improving the viscosity index, relative to the total weight of the lubricant composition.

[0107] Preferred additives for use in the lubricant composition according to the present invention include detergent additives, antiwear additives, extreme pressure additives, pour point improvers, defoamers, thickeners and mixtures thereof.

[0108] In a preferred manner, the lubricant composition according to the invention comprises at least one antiwear additive, at least one extreme pressure additive or a mixture thereof.

[0109] Antiwear additives and extreme pressure additives protect surfaces subject to friction by forming a protective film that adsorbs onto the surface.

[0110] There are many anti-wear additives. In a preferred manner, for the lubricant composition of the invention, the anti-wear additive is selected from phosphorus-sulfur additives, such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, more particularly zinc dialkyldithiophosphates or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR)(OR'))2, wherein R and R' are identical or different and independently represent an alkyl moiety, preferably an alkyl moiety containing 1 to 18 carbon atoms.

[0111] Phosphate amines are also anti-wear additives that can be used in the lubricant composition according to the invention. However, the phosphorus provided by these additives can act as a poison in the automotive catalytic system because it produces ash. This effect can be minimized by partially replacing the phosphate amines with additives that do not contain phosphorus, such as polysulfides, especially sulfur olefins.

[0112] Advantageously, the lubricant composition according to the invention may comprise 0.01% to 6% by weight, preferably 0.05% to 4% by weight, more preferably 0.1% to 2% by weight of antiwear additives and extreme pressure additives relative to the total weight of the lubricant composition.

[0113] Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive.

[0114] Antioxidant additives generally delay the degradation of lubricant compositions in use. Such degradation is most often manifested as the formation of deposits in the presence of sludge or an increase in the viscosity of the lubricant composition.

[0115] Antioxidant additives act in particular as free radical inhibitors or destructors of hydroperoxides. Commonly used antioxidant additives include phenolic antioxidants, amine antioxidant additives, phosphorus-sulfur antioxidant additives. Some such antioxidant additives, such as phosphorus-sulfur antioxidant additives, can produce ash. Phenolic antioxidant additives can be ashless or in the form of neutral or alkaline metal salts. Antioxidant additives can be particularly selected from hindered phenols, esters of hindered phenols and hindered phenols containing thioether bridges, diphenylamine, at least one C1-C 12 Alkyl partially substituted diphenylamines, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0116] Preferably, according to the present invention, the hindered phenol is selected from compounds comprising a phenolic moiety in which at least one carbon atom near the carbon atom carrying the alcohol functional group is blocked by at least one C1-C 10 Alkyl moieties are substituted, preferably C1-C6 alkyl moieties, preferably C4 alkyl moieties, preferably tert-butyl moieties.

[0117] Amine compounds are another class of antioxidant additives which can be used in combination with phenolic antioxidant additives, if appropriate. Examples of amine compounds are aromatic amines, for example having the formula NR a R b R c Aromatic amines, wherein R a represents an aliphatic part or an aromatic group which may be substituted, R b represents an aromatic moiety which may be substituted, R c represents a hydrogen atom, an alkyl moiety, an aryl moiety or a group having the formula R d S(O) z R e part, where R d represents an alkylene or alkenylene moiety, R e represents an alkyl moiety, an alkenyl moiety or an aryl moiety, and z represents 0, 1 or 2.

[0118] Sulfuralkylphenols or alkali metal salts or alkaline earth metal salts thereof may further be used as antioxidant additives.

[0119] Another class of antioxidant additives are copper compounds, such as copper thiophosphates or dithiophosphates, copper salts and carboxylates, copper dithiocarbamates, copper sulfonates, copper phenates, copper acetylacetonate. Copper salts I and II, succinates or succinic anhydride salts can also be used.

[0120] The lubricant composition according to the invention may further comprise any type of antioxidant known to a person skilled in the art.

[0121] Advantageously, the lubricant composition according to the invention comprises at least one ashless antioxidant additive.

[0122] Further advantageously, the lubricant composition according to the invention comprises from 0.1% to 2% by weight of at least one antioxidant additive, relative to the total weight of the composition.

[0123] The lubricant composition according to the invention may further comprise at least one detergent additive.

[0124] Detergent additives generally reduce the formation of deposits on the surfaces of metal parts by dissolving oxidation and combustion byproducts.

[0125] Detergent additives that can be used in the lubricant composition according to the present invention are generally known to those skilled in the art. The detergent additive can be an anionic compound comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali metal or an alkaline earth metal.

[0126] The detergent additive is preferably selected from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates and phenates. The alkali metal and alkaline earth metal are preferably calcium, magnesium, sodium or barium.

[0127] Such metal salts typically include a stoichiometric or excess amount (i.e., a concentration greater than a stoichiometric amount) of the metal. This is also true for overbased detergents; the excess metal that imparts the overbased character to the detergent additive is typically in the form of an oil-insoluble metal salt, such as a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate.

[0128] Advantageously, the lubricant composition according to the invention may comprise from 0.5% to 8% by weight or from 2% to 4% by weight of detergent additives relative to the total weight of the lubricant composition.

[0129] Further advantageously, the lubricant composition according to the invention further comprises at least one pour point depressant additive.

[0130] According to the present invention, pour point depressant additives generally improve the performance of lubricant compositions under cold conditions by slowing the formation of paraffin crystals.

[0131] Examples of pour point depressant additives include alkyl polymethacrylates, polyacrylates, polyaromatic amides, polyalkylphenols, polyalkylnaphthalenes, alkyl polystyrenes.

[0132] According to one embodiment, the lubricant composition according to the invention further comprises at least one dispersant. This dispersant is used to maintain suspension and remove insoluble solid contaminants consisting of oxidation byproducts formed when the lubricant composition is used. The dispersant can be selected from Mannich bases, succinimide and derivatives thereof, such as derivatives of polyisobutylene succinic anhydride, polyolefin amide enamine polyols.

[0133] Preferably, the lubricant composition according to the invention comprises 0.5% to 4.5% by weight, preferably 1% to 2.5% by weight, of dispersant, relative to the total weight of the lubricant composition.

[0134] The invention further relates to the use of a lubricant composition according to the invention for lubricating parts of an engine, such as an engine of a motor vehicle, more particularly an engine of a plug-in hybrid vehicle or an engine of a hybrid vehicle including a range extender.

[0135] The invention also relates to the use of a lubricant composition according to the invention as defined above for reducing friction between engine components.

[0136] The invention also relates to the use of a lubricant composition according to the invention as defined above for reducing the fuel consumption of an engine.

[0137] The invention also relates to a method for lubricating the engine of a plug-in hybrid vehicle or of a hybrid vehicle comprising a range extender, comprising contacting at least one component of the engine with a lubricant composition according to the invention.

[0138] The invention also relates to a method for reducing the fuel consumption of a plug-in hybrid vehicle or a hybrid vehicle comprising a range extender, comprising contacting at least one mechanical part of the engine with a lubricant composition as defined above.

[0139] The present invention also relates to a method of reducing friction occurring in an engine, said method comprising using the lubricant composition of the present invention.

[0140] The composition is preferably as described above.

[0141] The present invention also relates to a method for improving the fuel economy (FE or fuel eco) performance of a lubricant composition, said method comprising using at least one diester of formula (I) and at least one Group II+ base oil as defined above.

[0142] Various aspects of the invention may be illustrated by the following examples. DETAILED DESCRIPTION

[0143] Example 1 : Preparation of lubricant composition

[0144] The following lubricant compositions (CL compositions of the invention and CC comparative compositions) were prepared according to methods known to those skilled in the art.

[0145] The composition is shown in Table 2 below:

[0146] [Table 2]

[0147]

[0148] The parameters of the lubricant compositions shown in Table 2 above are given in Table 3 below:

[0149] [Table 3]

[0150]

[0151] HTHS (High Temperature, High Shear) viscosity is a measure of the residual oil film viscosity at high temperature and high stress (shear under mechanical pressure). In this context, the HTHS100 viscosity value is measured at 100°C.

[0152] This value is measured according to standard CEC L-036-90 or ASTM D4683.

[0153] BOV is the viscosity of the base oil mixture at 100°C (in mm 2 / s).

[0154] Example 2 : Results related to fuel economy performance

[0155] The test was conducted on a Suzuki K12C (1.2L 4-cylinder) engine (without combustion). The friction of the engine (drag torque in Nm) was measured, which varies depending on the lubricant used. The gain in friction was then converted into fuel consumption (fuel economy).

[0156] K12C is an engine from the manufacturer Maruti-Suzuki. The engine is made of aluminum alloy, 1.2L displacement, 4-cylinder gasoline cylinder block. It is equipped with chain drive timing, double overhead camshafts, 16 valves with variable intake and exhaust timing control.

[0157] The engine friction (resistance torque in Nm) is measured, which varies depending on the lubricant used. The gain in friction is then converted into fuel consumption (fuel economy).

[0158] The results are given in Table 4 below and show the friction savings (expressed in %, relative to the reference oil) for the composition of Example 1 as a function of temperature.

[0159] The reference oil is a "standard" 0W-8 with the same additives as the oil 0W-20 GF-6. Its BOV is 4.1, and its viscosity at 100°C is 5.2, and its HTHS at 150°C is 1.80.

[0160] [Table 4]

[0161]

[0162] The CL lubricant composition significantly reduces friction on the K12C engine due to better lubrication, more specifically at colder temperatures, which is more advantageous on engines of plug-in hybrid vehicles or hybrid vehicles including range extenders. The fuel savings calculated for the CL lubricant composition in the NEDC cycle are also greater than for the other oils (CC1-CC3).

Claims

1. A lubricant composition comprising: - at least one diester of formula (I): R a -C(O)-O-([C(R)2] n -O) s -C(O)-R b (I) in: .R groups independently of one another represent a hydrogen atom or a straight-chain or branched alkyl group containing 1 to 5 carbon atoms, in particular a methyl group, an ethyl group or a propyl group, preferably a methyl group; .s means 1 or 2; .n represents 1, 2, or 3, provided that when s is different from 1, n may be the same or different: .R a and R b may be identical or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms; Provided that, when s is equal to 2 and ns is likewise equal to 2, at least one R group represents a straight or branched chain alkyl group having 1 to 5 carbon atoms; as well as Provided that, when s is equal to 1 and n is equal to 3, at least one R group bonded to the carbon in the beta position to the oxygen atom of the ester functional group represents a hydrogen atom, and - At least one Group II+ base oil having a kinematic viscosity of less than 12 cSt measured at 40°C according to ASTM D445, a kinematic viscosity of less than 3 cSt measured at 100°C according to ASTM D445 and a sulfur content less than or equal to 5 ppm.

2. The lubricant composition according to claim 1, comprising 15% to 90% by weight, preferably 25% to 85% by weight, in particular 40% to 80% by weight, of the diester of formula (I), relative to the total weight of the lubricant composition.

3. The lubricant composition according to claim 1 or 2, wherein The diester of formula (I) is a diester of the following formula (I'): R a -C(O)-O-([C(R)2] n -O)([C(R')2] m -O) s-1 -C(O)-R b (I’) in: .R and R' independently represent a hydrogen atom or a straight or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl group, an ethyl group or a propyl group, preferably a methyl group; .s means 1 or 2; .n means 2; .m means 2; .R a and R b may be identical or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms; Provided that, when s is equal to 2, at least one of the radicals R and R' represents a straight-chain or branched alkyl radical containing 1 to 5 carbon atoms.

4. The lubricant composition according to any one of claims 1 to 3, comprising 5% to 60% by weight, preferably 8% to 40% by weight, in particular 10% to 30% by weight, of base oil, relative to the total weight of the dispersion.

5. The lubricant composition according to any one of claims 1 to 4, wherein Said base oil has a content of aromatic compounds less than or equal to 2% by weight relative to the total weight of said base oil, said content being preferably zero.

6. The lubricant composition according to any one of claims 1 to 5, wherein The base oil has a content of paraffin compounds less than or equal to 85% by weight, preferably less than or equal to 80% by weight, relative to the total weight of the base oil.

7. The lubricant composition according to any one of claims 1 to 6, wherein The base oil has a content of cycloparaffinic compounds less than or equal to 30% by weight, preferably less than or equal to 25% by weight, relative to the total weight of the base oil.

8. The lubricant composition according to any one of claims 1 to 7, further comprising a friction modifier additive, preferably containing molybdenum.

9. Use of a lubricant composition according to any one of claims 1 to 8 for lubricating parts of an engine of a motor vehicle.

10. Use according to claim 9 for reducing friction between components of the engine and / or for reducing fuel consumption of the engine.

11. A method for lubricating an engine of a plug-in hybrid vehicle or an engine of a hybrid vehicle including a range extender, comprising contacting at least one mechanical part of the engine with a lubricant composition according to any one of claims 1 to 8.

12. A method of reducing fuel consumption of a plug-in hybrid vehicle or a hybrid vehicle including a range extender, the method comprising contacting at least one mechanical component of the engine with a lubricant composition according to any one of claims 1 to 8.

Images