Lubricant compositions with improved fuel economy properties in hybrid vehicles

Abstract

The present invention is a -C(O)-O-([C(R)2] n -O) s -C(O)-R b and at least one Group II+ base oil having a kinematic viscosity as measured at 40°C according to ASTM D445 of less than 12 cSt, a kinematic viscosity as measured at 100°C according to ASTM D445 of less than 3 cSt, and a sulfur content of 5 ppm or less. The present invention also relates to the use of said lubricant composition for lubricating parts of an automobile engine.

Description

[Technical Field]

[0001] The subject of the present invention relates to lubricant compositions for use in light vehicles, especially hybrid vehicles, more especially hybrid vehicles of the plug-in hybrid vehicle type and hybrid vehicles with range extenders. A further subject of the present invention is to improve the low-temperature fuel economy of the engines of such vehicles. [Background technology]

[0002] A hybrid vehicle has two prime movers: 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. A battery provides the electricity needed to operate the electric motor. In conventional hybrid vehicles, the battery is charged during braking and deceleration by a kinetic energy recovery system (KERS) built into the vehicle.

[0003] There are different hybrid vehicle technologies. Hybrid technologies include: - Micro-hybrid vehicles (also known as light hybrids), vehicles with a "stop-start" system, can recover energy generated by braking to charge a battery that can temporarily assist the engine. - Mild hybrid vehicles, which include electric assist during acceleration, and - A full hybrid vehicle is a vehicle with complete hybridization. At low speeds, when the battery is charging, the electric motor is responsible for starting and moving. At high speeds, or when the battery is discharging, the internal combustion engine takes over, and when increased power is needed (for example, when accelerating), the two prime movers work together. It is therefore possible to drive for several kilometers with the internal combustion engine off.

[0004] Other complementary technologies, namely plug-in hybrid vehicles and hybrid vehicles with range extenders, have been developed in recent years. Plug-in hybrid vehicles (also known as plug-in hybrids) include an internal combustion engine and an electric motor; the battery can be charged from a power source; such vehicles can therefore be driven in 100% electric mode for distances of several tens of kilometers, for example, 50 kilometers. In hybrid vehicles with range extenders, 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, approximately 30%), the engine starts and drives a current generator to produce the electricity needed to charge the battery and keep the electric motor running.

[0005] In both types of hybrid vehicles, the internal combustion engines operate at lower temperatures (around 40°C or below) than engines in other types of hybrid vehicles, particularly due to their less frequent use. However, at low temperatures, conventional lubricant compositions become more viscous and additives are not as active as in conventional applications at higher temperatures. Current lubricants are optimized to conserve fuel consumption at high temperature conditions.

[0006] The need for high performance lubricant compositions is increasing, especially with regard to improving the energy efficiency of a lubricant composition, more especially its fuel economy or fuel eco, for short (FE), i.e., reducing the fuel consumption of engines, more especially engines of hybrid vehicles.

[0007] The ultimate goal of improving the FE is, in particular, to obtain a lubricant composition that is as flowable as possible and therefore has a low viscosity, which may be correlated with a low grade. Summary of the Invention [Problem to be solved by the invention]

[0008] It is thus an object of the present invention to provide a lubricant composition for lubricating the engine of a plug-in hybrid vehicle or a hybrid vehicle with a range extender, which has improved fuel economy characteristics.

[0009] Another object of the present invention is to provide a lubricant composition for engines of light duty vehicles, particularly hybrid vehicles, which exhibits improved fuel economy characteristics at low temperatures. [Means for solving the problem]

[0010] Accordingly, the present invention relates to a lubricant composition comprising: at least one diester having the formula (I): R a -C(O)-O-([C(R)2] n -O) s -C(O)-R b (I) In the formula: the R groups, independently of one another, represent a hydrogen atom or a linear or branched alkyl group containing 1 to 5 carbon atoms, in particular a methyl, ethyl or propyl group, preferably methyl; s stands for 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, with the proviso that when s is equal to 2 and n is the same and equal to 2, at least one of the R groups represents a linear or branched alkyl group having 1 to 5 carbon atoms; and provided that when s is equal to 1 and n is equal to 3, at least one of the R groups attached to the carbon atom beta 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, measured according to ASTM D445 at 40°C, of ​​less than 12 cSt, a kinematic viscosity, measured according to ASTM D445 at 100°C, of ​​less than 3 cSt, and a sulfur content of 5 ppm or less.

[0011] The lubricant compositions according to the invention are thus based on the combination of at least one specific group II+ base oil as defined above with at least one diester of formula (I).

[0012] Surprisingly, such compositions have been found to provide improved fuel economy properties, particularly in the presence of molybdenum-based friction modifiers, despite the incompatibility associated with the use of esters.

[0013] [Diester having formula (I)] According to one embodiment, the diesters of the invention correspond to formula (I) as defined above, in which if s is different from 1, all n are the same.

[0014] Preferably, in the diesters of formula (I) of the present invention, n represents 2 or 3, preferably 2.

[0015] Preferably, in formula (I), at least one of the R groups represents a linear or branched alkyl group containing from 1 to 5 carbon atoms, preferably from 1 to 4 carbon atoms, more preferably methyl, ethyl or propyl, advantageously methyl.

[0016] According to one particular embodiment, the diester of formula (I) according to the invention is a diester having 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 the formula: R and R' independently represent a hydrogen atom or a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl, ethyl or propyl group, preferably a methyl group; s stands for 1 or 2, n represents 2, m stands for 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 R and R' groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms.

[0017] Advantageously, at least one of the R or R' groups in the diester of formula (I') represents a linear or branched alkyl group containing from 1 to 5 carbon atoms, preferably from 1 to 4 carbon atoms, preferably methyl, ethyl or propyl, advantageously methyl.

[0018] Preferably, in the compounds of formula (I) and (I'), R a and R b has a linear chain of 7 to 14 carbon atoms, preferably 8 to 12 carbon atoms.

[0019] In one particular embodiment, s represents 2 in formula (I) or formula (I').

[0020] The diesters of the present invention are preferably compounds of formula (I'a): R a -C(O)-O-([C(R)2] n -O)-([C(R')2] m -O)-C(O)-R b (I'a) In the formula: R and R' independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl; n represents 2, m stands for 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, However, at least one of the R or R' groups represents a linear or branched alkyl group having 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl.

[0021] Preferably, at least one of the R groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl, and at least one of the R' groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl.

[0022] Even more preferably, in formula (I'a), one of the R groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl, one of the R' groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl, and the other R and R' groups represent a hydrogen atom.

[0023] In one particular embodiment, the diester of the present invention is a compound of formula (I''a): R a -C(O)-O-CHR 1 -CHR 2 -O-CHR 3 -CHR 4 -OC(O)-R b (I''a) In the formula: R 1 Groups and R2 one of the groups represents a linear or branched alkyl group having 1 to 5 carbon atoms, and the other represents a hydrogen atom; R 3 Groups and R 4 one of the groups represents a linear or branched alkyl group having 1 to 5 carbon atoms, and the other represents a hydrogen atom; R a and R b are the same or different and are as defined above.

[0024] Preferably, in formula (I''a), R 1 Groups and R 2 one of the groups represents a methyl, ethyl or propyl group, preferably methyl, and the other represents a hydrogen atom, R 3 Groups and R 4 One of the groups represents a methyl, ethyl or propyl group, preferably methyl, and the other represents a hydrogen atom.

[0025] According to another embodiment, in formula (I) or (I'), s represents 1 and the diester of the invention is of formula (I'b): R a -C(O)-O-([C(R)2] n -O)-C(O)-R b (I'b) In the formula: R and R independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl; n represents 2, R a and R b may be the same or different and independently represent a linear or branched, saturated or unsaturated hydrocarbon moiety having a linear chain of 6 to 18 carbon atoms.

[0026] Preferably, in formula (I'b), at least one of the R groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl.

[0027] Preferably, in formula (I'b), one of the R groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably methyl, ethyl or propyl, preferably methyl, and the other represents a hydrogen atom.

[0028] Within the framework of the present invention, the expression "comprising x to y carbon atoms" must be understood to include the boundaries x and y.

[0029] Within the framework of the present invention, the term "linear chain of x to y carbon atoms" is to be understood as a saturated or unsaturated, preferably saturated, carbon chain which in turn comprises x to y carbon atoms, carbon atoms which may be present at branching levels of the carbon chain being disregarded in the number of carbon atoms (x to y) forming the linear chain.

[0030] According to one particular embodiment, in formula (I), (I'), (I'a), (I''a) or (I'b), R a and R b may be the same or different and may be of plant, animal or petroleum origin.

[0031] According to one particular embodiment, in formula (I), (I'), (I'a), (I''a) or (I'b), R a and R b can be the same or different and represent saturated moieties.

[0032] According to one particular embodiment, in formula (I), (I'), (I'a), (I''a) or (I'b), R a and R b represent linear moieties, whether identical or different. More particularly, R a and R bmay be the same or different and represent saturated straight-chain hydrocarbon moieties 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 to 12 carbon atoms.

[0033] According to another preferred embodiment, in formula (I), (I'), (I''a), (I'a) or (I'b), R a and R b may be the same or different and represent saturated linear alkyl groups containing 6 to 18 carbon atoms, preferably 7 to 17 carbon atoms, particularly 7 to 14 carbon atoms, preferably 8 to 12 carbon atoms, particularly 9 to 12 carbon atoms.

[0034] Preferably, R a and R b are identical.

[0035] The diesters of formula (I) may be commercially available or may be prepared according to synthetic methods described in the literature and known to those skilled in the art, in particular according to the methods described in WO 2019 / 025446.

[0036] 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.

[0037] [II+ group base oil] According to one embodiment, said group II+ base oils have an aromatics content of less than or equal to 2% by weight relative to the total weight of the base oil, said content being preferably zero.

[0038] Preferably, the above group II+ base oils have a paraffinic compound content of not more than 85% by weight, preferably not more than 80% by weight, relative to the total weight of the base oil.

[0039] Preferably, the above group II+ base oils have a naphthenic content of not more than 30% by weight, preferably not more than 25% by weight, relative to the total weight of the base oil.

[0040] The KV40 and KV100 of the base oil are measured according to the ASTM D445 standard.

[0041] As described above, the base oil has a KV40 (kinematic viscosity measured at 40° C.) of 12 cSt or less.

[0042] As described above, the base oil has a KV100 (kinematic viscosity measured at 100°C) of 3 cSt or less.

[0043] Preferably, the sulfur content of the base oil is 0.00001 to 5 ppm, more preferably 0.0001 to 1 ppm.

[0044] The content is measured according to the ASTM D2622 standard.

[0045] 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 base oil of group II+ as defined above, relative to the total weight of the lubricant composition.

[0046] Preferably, the lubricant composition according to the present invention has a grade according to the SAEJ300 classification of the XW-(Y) type, where X represents 0, 5 or 10, and Y represents an integer from 6 to 50, preferably 8 or 40, and preferably X=0 and Y=8.

[0047] The Noack volatility at 250°C is measured according to the method of CEC L-40-A-93. Preferably, the Noack volatility at 250°C of the lubricant composition of the present invention is 10 to 20%, preferably 12 to 15%.

[0048] The lubricant composition according to the present invention may further comprise compounds or additives other than the above-mentioned Group II+ base oil and diester of formula (I).

[0049] According to one particular embodiment, the lubricant composition of the present invention comprises an additional base oil different from the Group II+ base oils defined above.

[0050] The additional base oils used in the lubricant compositions of the present invention may be selected from among the oils of mineral or synthetic origin belonging to groups I to V according to the classes defined by the API classification (or their equivalents according to the ATIEL classification) (Table 1) or mixtures thereof.

[0051] [Table 1]

[0052] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil followed by subsequent refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0053] Mixtures of synthetic and mineral oils may also be used.

[0054] The additional base oil of the lubricant composition according to the present invention may further be selected from synthetic oils such as certain esters of carboxylic acids and alcohols and polyalphaolefins. The polyalphaolefins used as base oils may, for example, have a viscosity of 1.5 to 15 mm at 100°C according to the ASTM D445 standard. 2 They are obtained from monomers containing 4 to 32 carbon atoms, such as octene or decene, with a molar mass of 1 / s. Their average molar mass is generally between 250 and 3000 according to the ASTM D5296 standard.

[0055] The composition of the present invention may further comprise at least one additive.

[0056] Many additives may be used in the lubricant compositions of the present invention.

[0057] According to one embodiment, the lubricant composition according to the present invention further comprises a friction modifying additive, preferably containing molybdenum.

[0058] Preferably, the lubricant composition according to the present invention contains at least one friction modifying additive. Friction modifying additives help limit friction by forming an adsorbed monolayer on the surface of the metal in contact with them. The additive may be selected from metal-donating compounds and ashless compounds. Metal-donating compounds include transition metal complexes of Mo, Sb, Sn, Fe, Cu, and Zn, where the ligands may be hydrocarbon compounds containing oxygen, nitrogen, sulfur, or phosphorus atoms. Ashless friction modifying additives are generally of organic origin and may be selected from esters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty epoxide borates, amine acids, or fatty acid glycerol esters, which are different from the monoesters required according to the present invention. According to the present invention, the fatty compound contains at least one hydrocarbon moiety containing 10 to 24 carbon atoms. More particularly, the molybdenum compound may be selected from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof. Advantageously, the lubricant composition according to the invention may comprise from 0.01 to 10% by weight or from 0.01 to 5% by weight, preferably from 0.01 to 2% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight, of friction modifying additive relative to the total weight of the lubricant composition.

[0059] The molybdenum (Mo) in the lubricant composition of the present invention is provided by an organo-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).

[0060] Molybdenum dithiocarbamate compounds (MoDTC compounds) are complexes formed of a metal core bound to one or more ligands independently selected from alkyldithiocarbamate moieties. The MoDTC compounds of the compositions used in accordance with the present invention can contain 0.01 to 5 wt. % molybdenum, preferably 0.1 to 1.5 wt. % molybdenum, relative to the total mass of the MoDTC compound.

[0061] Preferably, the composition according to the invention comprises a friction modifying additive containing molybdenum, preferably comprising (effective content) 1 to 1000 ppm, preferably 400 to 600 ppm Mo by weight of the lubricant composition.

[0062] According to one embodiment, the lubricant composition may further comprise at least one viscosity index (VI) improving additive. Viscosity index improvers, and more particularly viscosity index improving polymers, provide good cold weather resistance and minimal viscosity at high temperatures. Examples of viscosity index improving polymers include polymeric esters, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene, and isoprene, homopolymers or copolymers of olefins such as ethylene or propylene, polyacrylates and polymethacrylates (PMAs), preferably copolymers, homopolymers, or polymethacrylates of olefins such as ethylene or propylene.

[0063] More particularly, the lubricant composition according to the invention may contain 1 to 15% by weight, preferably 5 to 10% by weight, of a viscosity index improving additive relative to the total weight of the lubricant composition.

[0064] Preferred additives for lubricant compositions according to the present invention include detergent additives, anti-wear additives, extreme pressure additives, pour point improvers, anti-foam agents, thickeners and mixtures thereof.

[0065] Preferably, the lubricant composition according to the present invention comprises at least one anti-wear additive, at least one extreme pressure additive, or a mixture thereof.

[0066] Anti-wear and extreme pressure additives protect surfaces subjected to friction by forming a protective film that is adsorbed onto the surface.

[0067] A wide variety of anti-wear additives exist. Preferably, for the lubricant compositions of the present invention, the anti-wear additive is selected from phosphorus-sulfur based additives such as metal alkylthiophosphates, particularly zinc alkylthiophosphates, and more particularly zinc dialkyldithiophosphate, or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR)(OR'))2, where R and R', the same or different, independently represent alkyl moieties, preferably alkyl moieties containing 1 to 18 carbon atoms.

[0068] Amine phosphates are also antiwear additives that may be used in the lubricant compositions of the present invention. However, the phosphorus provided by such additives can poison automotive catalyst systems by producing ash. This effect can be minimized by substituting a portion of the amine phosphates with phosphorus-free additives, such as polysulfides, especially sulfur olefins.

[0069] Advantageously, the lubricant composition according to the invention may comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% by weight of anti-wear and extreme pressure additives relative to the total weight of the lubricant composition.

[0070] Advantageously, the lubricant composition according to the invention may contain at least one antioxidant additive.

[0071] Antioxidant additives generally retard the deterioration of lubricant compositions during use, which is most often manifested as deposit formation, the presence of sludge, or an increase in the viscosity of the lubricant composition.

[0072] Antioxidant additives act specifically as hydroperoxide destroyers or radical inhibitors. Commonly used antioxidant additives include phenolic antioxidants, amine antioxidant additives, and phosphosulfuric antioxidant additives. Some of these antioxidant additives, such as phosphosulfuric antioxidant additives, may produce ash. Phenolic antioxidant additives may be ashless or in the form of neutral or basic metal salts. Antioxidant additives specifically include sterically hindered phenols, sterically hindered phenol esters, and sterically hindered phenols containing thioether bridges, diphenylamines, and esters of at least one C1-C 12 The alkyl moiety of the diphenylamine may be selected from N,N'-dialkyl-aryl-diamines, N,N'-dialkyl-aryl-diamines, and mixtures thereof.

[0073] Preferably, according to the present invention, the sterically hindered phenol has at least one C1-C2 carbon atom adjacent to the carbon atom carrying the alcohol functional group. 10 It is selected from compounds comprising a phenol moiety substituted by an alkyl moiety, preferably a C1-C6 alkyl moiety, preferably a C4 alkyl moiety, preferably a tert-butyl moiety.

[0074] Amine compounds are another class of antioxidant additives that may be used in combination with phenolic antioxidant additives, where appropriate. Examples of amine compounds include aromatic amines, such as NR a R b R c where R a represents an aliphatic moiety or an aromatic group which may be substituted, R b represents an aromatic moiety that may be substituted, and R c is a hydrogen atom, an alkyl moiety, an aryl moiety, or R d S(O) z R e represents a moiety having the chemical formula d represents an alkylene or alkenylene moiety, R erepresents an alkyl, alkenyl, or aryl moiety; and z represents 0, 1, or 2.

[0075] Sulfur alkylphenols or alkali metal or alkaline earth metal salts thereof may also be used as antioxidant additives.

[0076] 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 acetylacetonates. Copper(I) and copper(II) salts, succinates or succinic anhydrides may also be used.

[0077] The lubricant compositions of the present invention may further include any type of antioxidant known to those skilled in the art.

[0078] Advantageously, the lubricant composition according to the invention comprises at least one ashless antioxidant additive.

[0079] More 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.

[0080] The lubricant composition according to the present invention may further comprise at least one detergent additive.

[0081] Detergent additives generally reduce the formation of deposits on the surfaces of metal parts by dissolving oxidation and combustion by-products.

[0082] Detergent additives that can be used in the lubricant compositions of the present invention are generally known to those skilled in the art. Detergent additives can be anionic compounds containing a long oleophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali metal or alkaline earth metal.

[0083] The detergent additive is preferably selected from alkali or alkaline earth metal salts of sulfonates, salicylates, naphthenates, phenates, carboxylic acids, The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

[0084] Such metal salts generally contain the metal in a stoichiometric amount or in an excess amount, i.e., a concentration greater than the stoichiometric amount, which in this case is an overbased detergent, the excess metal imparting overbasing to the detergent additive generally being in the form of an oil-insoluble metal salt, such as carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate.

[0085] 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 additive relative to the total weight of the lubricant composition.

[0086] More advantageously, the lubricant composition according to the invention further comprises at least one pour point depressant additive.

[0087] By slowing down the formation of paraffin crystals, pour point depressant additives generally improve the behavior of the lubricant compositions of the present invention under low temperature conditions.

[0088] Examples of pour point depressant additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkyl polystyrenes.

[0089] In one embodiment, the lubricant composition further comprises at least one dispersant, which helps to keep in suspension and expel insoluble solid contaminants consisting of oxidation by-products formed during use of the lubricant composition. The dispersant may be selected from Mannich bases, succinimides and their derivatives, such as polyisobutylene succinic anhydride derivatives, and polyolefinamide alkeneamine polyols.

[0090] Preferably, the lubricant composition according to the invention comprises 0.5 to 4.5% by weight of dispersant, preferably 1 to 2.5% by weight of dispersant relative to the total weight of the lubricant composition.

[0091] The present invention further relates to the use of the 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 with a range extender.

[0092] The present invention further relates to the use as defined above of a lubricant composition according to the invention for reducing friction between parts of an engine.

[0093] The present invention further relates to the above-defined use of the lubricant composition according to the invention for reducing the fuel consumption of an engine.

[0094] The present invention further relates to a method for lubricating an engine of a plug-in hybrid vehicle or an engine of a hybrid vehicle having a range extender, the method comprising contacting at least one component of the engine with a lubricant composition according to the present invention.

[0095] The present invention further relates to a method for reducing fuel consumption in a plug-in hybrid vehicle or a hybrid vehicle with a range extender, the method comprising contacting at least one mechanical part of the engine with a lubricant composition as defined above.

[0096] The present invention further relates to a method for reducing friction occurring in an engine, said method comprising the use of a lubricant composition according to the present invention.

[0097] The composition is preferably as described above.

[0098] The present invention further relates to a method for improving the fuel economy (FE or fuel eco) properties of a lubricant composition, said method comprising the use of at least one diester of formula (I) as defined above and at least one group II+ base oil.

[0099] Different aspects of the present invention can be illustrated by the following examples. DETAILED DESCRIPTION OF THE INVENTION

[0100] Example 1: Preparation of lubricant composition The following lubricant compositions (Composition CL according to the invention and Comparative Composition CC) are prepared according to methods known to those skilled in the art.

[0101] The compositions are shown in Table 2 below.

[0102] [Table 2]

[0103] The parameters of the lubricant compositions shown in Table 2 above are shown in Table 3 below.

[0104] [Table 3]

[0105] HTHS (High Temperature, High Shear) viscosity is a measure of the viscosity of a residual oil film subjected to high stress (shear due to mechanical pressure) at high temperature, where the HTHS 100 viscosity value is measured at 100°C.

[0106] The values ​​are measured according to the CEC L-036-90 standard or the ASTM D4683 standard.

[0107] BOV is the calculated viscosity (mm 2 / s).

[0108] Example 2: Results regarding fuel economy characteristics A Suzuki K12C (1.2L, 4-cylinder) engine was subjected to a pull test (without combustion). Engine friction (resistance torque, in Nm) was measured, which varied depending on the lubricant used. The gain in terms of friction was then converted into fuel consumption (fuel economy).

[0109] The K12C is a Maruti Suzuki engine. It is a 1.2L, 4-cylinder, aluminium alloy petrol engine block. It has 16 valves with timing drive chain, double overhead camshafts and variable intake and exhaust timing control.

[0110] The engine friction (resisting torque, in Nm) was measured, which varied depending on the lubricant used, and the gain in terms of friction was converted into fuel consumption (fuel economy).

[0111] The results are shown in Table 4 below, which shows the savings in terms of friction as a function of temperature for the composition of Example 1, expressed as a percentage (relative to the reference oil).

[0112] The reference oil was a "standard" 0W-8 with the same additives as the 0W-20 GF-6 oil. Its BOV was 4.1, its viscosity at 100°C was 5.2, and its HTHS at 150°C was 1.80.

[0113] [Table 4]

[0114] The CL lubricant composition significantly reduces friction in the K12C engine due to better lubrication, especially at lower temperatures, which is more favorable for engines of plug-in hybrid vehicles or hybrid vehicles with range extenders. The fuel economy calculated in the NEDC cycle is also greater for the CL lubricant composition than for the other oils (CC1 to CC3).

Claims

1. at least one diester having the formula (I), R ａ -C(O)-O-([C(R) ２ ] ｎ -O) ｓ -C(O)-R ｂ (I) In the formula: the R groups, independently of one another, represent a hydrogen atom or a linear or branched alkyl group containing 1 to 5 carbon atoms, in particular a methyl, ethyl or propyl group, preferably methyl; s represents 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, with the proviso that when s is equal to 2 and n is the same and equal to 2, at least one of the R groups represents a linear or branched alkyl group having 1 to 5 carbon atoms; and provided that when s is equal to 1 and n is equal to 3, at least one of the R groups attached to the carbon atom beta 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, measured according to ASTM D445 at 40°C, of ​​less than 12 cSt and a kinematic viscosity, measured according to ASTM D445 at 100°C, of ​​less than 3 cSt and a sulfur content of less than or equal to 5 ppm; A lubricant composition comprising:

2. 2. 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 diester of formula (I), relative to the total weight of the lubricant composition.

3. The diester of formula (I) is a diester of 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 the formula: R and R' represent, independently of one another, a hydrogen atom or a linear or branched alkyl group containing 1 to 5 carbon atoms, preferably a methyl, ethyl or propyl group, preferably a methyl group; s represents 1 or 2, n represents 2, m represents 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, with the proviso that when s is equal to 2, at least one of the R and R' groups represents a linear or branched alkyl group containing 1 to 5 carbon atoms; 3. The lubricant composition of claim 1, which is a diester.

4. 4. 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 composition.

5. 5. A lubricant composition according to any one of claims 1 to 4, wherein the base oil has an aromatics content of not more than 2% by weight relative to the total weight of the base oil, the content being preferably zero.

6. 6. Lubricant composition according to any one of claims 1 to 5, wherein the base oil has a paraffinic compounds content of not more than 85 wt. %, preferably not more than 80 wt. %, relative to the total weight of the base oil.

7. 7. Lubricant composition according to any one of claims 1 to 6, wherein the base oil has a naphthenic compounds content of not more than 30% by weight, preferably not more than 25% by weight, relative to the total weight of the base oil.

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

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

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

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

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

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