HIGH VISCOSITY INDEX LUBRICANTS

Abstract

HIGH VISCOSITY INDEX LUBRICATING COMPOSITIONS The present invention relates to a lubricating composition comprising: - a viscosity index improving additive; and - a mixture of at least one first Group IV base oil and one second Group IV base oil, wherein: . the first Group IV base oil has a kinematic viscosity measured at 100°C, according to ASTM D445, strictly less than 3 mm² / s, and . the second Group IV base oil, different from the first Group IV base oil, has a kinematic viscosity measured at 100°C, according to ASTM D445, less than or equal to 3.5 mm² / s and has a Noack volatility, determined according to CEC L-40-93, strictly less than 14%. Figure for abstract: none

Description

Title of the invention: HIGH VISCOSITY INDEX LUBRICANT COMPOSITIONS

[0001] The present invention relates to lubricating compositions having a high viscosity index, making it possible to obtain high fuel economy performance (Fuel Eco properties).

[0002] Lubricating compositions, also called "lubricants", are commonly used in the various components of motor vehicles for the main purpose of reducing the friction forces between the various moving metal parts in these components, in particular the engine, the transmission and the hydraulic circuit. They are also effective in preventing premature wear or even damage to these parts, and in particular to their surface. To do this, a lubricating composition is conventionally composed of a base oil with which several additives are generally associated, designed to stimulate the lubricating performance of the base oil, such as, for example, friction-modifying additives, but also to provide additional performance.

[0003] The need for high-performance lubricating compositions is increasing, particularly with regard to energy efficiency and more particularly the improvement of Fuel Economy or Fuel Eco in abbreviated form (FE) of lubricating compositions or the reduction of fuel consumption of engines.

[0004] The objective for improving the FE is in particular to have lubricating compositions that are as fluid as possible, and therefore have a low viscosity possibly correlated with a low grade.

[0005] The aim of the invention is then to propose a lubricating composition with a high viscosity index and also making it possible to reduce fuel savings. Another aim of the invention is to provide a lubricating composition with a reduced carbon footprint.

[0006] To this end, the invention relates to a lubricating composition comprising:

[0007] - a viscosity index improving additive; and

[0008] - a mixture of at least a first group IV base oil and a second Group IV base oil, in which:

[0009] . the first group IV base oil has a measured kinematic viscosity at 100°C, according to ASTM D445 standard, strictly less than 3 mm2 / s, and

[0010] . the second group IV base oil, different from the first group IV base oil group IV, has a kinematic viscosity measured at 100°C, according to standard ASTM D445, less than or equal to 3.5 mm2 / s and has a Noack volatility, determined according to CEC L-40-93 standard, strictly less than 14%.

[0011] The lubricating composition according to the invention, as demonstrated later in the examples, makes it possible to meet precise specifications concerning certain parameters, such as in particular the kinematic viscosity at 40°C, the kinematic viscosity at 144°C and the Noack volatility at 250°C.

[0012] Typically, the specific choice of the combination of the viscosity index improving additive with the mixture of two particular group IV base oils makes it possible to obtain a lubricating composition advantageously having a kinematic viscosity at 40°C strictly lower than 23.5 mm2 / s, a kinematic viscosity at 144°C strictly greater than 3.8 mm2 / s and a Noack volatility at 250°C less than 22%.

[0013] According to one embodiment, the lubricating composition according to the invention has a grade XW-Y according to the SAE J300 classification, X being equal to 0, 5 or 10 and Y being from 16 to 50, preferably from 16 to 40, in particular equal to 16 or 20.

[0014] Preferably, the lubricating composition according to the invention has a grade OW-16 or 0W-20.

[0015] According to one embodiment, the kinematic viscosity measured at 40°C, according to the ASTM D445 standard of the lubricating composition according to the invention is between 22 and 23.5 mm2 / s, in particular between 22.5 and 23.5 mm2 / s, preferably between 22.6 and 23 mm2 / s.

[0016] According to one embodiment, the lubricating composition has a kinematic viscosity measured at 100°C, according to the ASTM D445 standard, of 6 to 7 mm2 / s, preferably 6.8 to 6.9 mm2 / s.

[0017] According to one embodiment, the kinematic viscosity at 144°C of said lubricating composition according to the invention is from 3.8 to 4 mm2 / s, preferably from 3.85 to 3.9 mm2 / s. This parameter is for example determined by calculation according to the measured values ​​of the kinematic viscosity at 40°C (KV40) and the kinematic viscosity at 100°C (KV100), in particular by applying the Walther and Mac Coull relationship.

[0018] According to one embodiment, the Noack volatility, determined according to the CEC L-40-93 standard, of the lubricating composition according to the invention is between 18% and 22%, preferably between 18% and 19%.

[0019] The Noack volatility of the lubricating composition corresponds to the Noack volatility at 250°C, measured according to the CEC L-40-A-93 method.

[0020] According to one embodiment, the viscosity index of the lubricating composition according to the invention is greater than 290, in particular greater than 292.

[0021] The viscosity index is calculated by measuring the kinematic viscosity at 40°C and 100°C. These measurements are then compared to the results of two reference oils. Its calculation method is described in the ASTM D2270 standard.

[0022] According to one embodiment, the lubricating composition according to the invention has a viscosity at 135°C and under constant shear (or HTHS 135), after having been subjected to a shear test over 42 cycles and having been mixed with 7% gasoline, of between 2.25 and 2.6 mPa.s, preferably between 2.4 and 2.6 mPa.s, and preferably between 2.5 and 2.55 mPa.s.

[0023] This parameter is measured according to the method described below:

[0024] - the lubricating composition is subjected to a shear test for 42 cycles (according to ASTM D6278-20a “Standard Test Method for Shear Stability of Polymer Containing Fluids Using a European Diesel Injector Apparatus”);

[0025] - the sheared lubricating composition is then mixed with gasoline (SP85) in a content equal to 7% by weight relative to the total weight of said sheared lubricating composition; and

[0026] - the viscosity at 100°C and under constant shear (or HTHS 100) of the composition resulting is measured according to CEC L-036-90 or ASTM D4683 standards;

[0027] - the viscosity at 150°C and under constant shear (or HTHS 150) of the composition resulting is measured according to CEC L-036-90 or ASTM D4683 standards; and

[0028] - the viscosity at 135°C and under constant shear (or HTHS 135) of said com position is then calculated.

[0029] This parameter allows to define a minimum viscosity not to be exceeded in order to avoid a risk of engine failure. The measurement of HTHS at 150°C on a new oil simulates the behavior of the oil in the contact of the connecting rod head, the bearing and the crankshaft. The sheared oil (during 42 cycles as indicated above) is polluted by fuel (as after a certain number of kilometers of use) with a measurement made at 135°C.

[0030] According to one embodiment, the lubricating composition has a viscosity at 150°C and under constant shear (or HTHS 150) greater than or equal to 2.3 mPa.s, preferably between 2.35 and 2.38 mPa.s.

[0031] HTHS (High Temperature, High Shear) viscosity is a measure of the viscosity of the residual oil film under high stress (shearing under mechanical pressure) at high temperature. Here, the HTHS viscosity value 150 is measured at 150°C.

[0032] These values ​​are measured according to CEC L-036-90 or ASTM D4683 standards. Base oils

[0033] As indicated above, the lubricating composition comprises in particular a mixture of base oils, namely at least two different base oils.

[0034] According to the present application, the term "base oil mixture" means the aforementioned mixture of at least a first group IV base oil and a second group IV base oil, these two base oils being different.

[0035] According to one embodiment, the kinematic viscosity measured at 100°C, according to the standard ASTM D445, of the mixture of base oils of the lubricating composition according to the invention (BOV or viscosity of the mixture of base oils) is between 3 and 3.6 mm2 / s, in particular between 3 and 3.5 mm2 / s, preferably between 3.1 and 3.3 mm2 / s.

[0036] The mixture of base oils according to the invention comprises at least two different base oils of group IV, namely of the polyalphaolefin (PAO) type.

[0037] As indicated above, these two base oils differ, for example, in their kinematic viscosity measured at 100°C. First base oil

[0038] The first group IV base oil of the base oil mixture according to the invention has a kinematic viscosity (BOV1) measured at 100°C, according to the ASTM D445 standard, strictly less than 3 mm2 / s.

[0039] For example, BOV 1 is equal to 2 mm2 / s.

[0040] According to one embodiment, the content of first group IV base oil is from 0.1% to 15% by weight relative to the weight of said lubricating composition. Preferably, the content of first group IV base oil is from 1% to 10%, in particular from 5% to 8%, by weight relative to the weight of said lubricating composition. Second base oil

[0041] The second group IV base oil, different from the first group IV base oil, has a kinematic viscosity (BOV2) measured at 100°C, according to ASTM D445, less than or equal to 3.5 mm2 / s.

[0042] For example, BOV2 is equal to 3.5 mm2 / s.

[0043] The second base oil of the base oil mixture according to the invention furthermore has a Noack volatility, determined according to the CEC L-40-93 standard, strictly less than 14%.

[0044] The Noack volatility of this second base oil corresponds to the Noack volatility at 250°C, measured according to the CEC L-40-A-93 method.

[0045] According to one embodiment, the content of second group IV base oil is from 65% to 79.9% by weight relative to the weight of said lubricating composition. Preferably, the content of first group IV base oil is from 68% to 75%, in particular from 70% to 73%, by weight relative to the weight of said lubricating composition.

[0046] According to a particular embodiment, the lubricating composition of the invention comprises an additional base oil, different from the aforementioned group IV base oils.

[0047] The additional base oil used in the lubricating compositions of the invention may be chosen from oils of mineral or synthetic origin ap 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 their mixtures.

[0048] [Tables 1] Saturated substance content Sulphur content Viscosity index (VI) Group I Mineral oils <90% > 0.03% 80 < VI < 120 Group II Hydrocracked oils >90% < 0.03% 80 < VI < 120 Group III Hydro-isomerized oils >90% < 0.03% > 120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0049] 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.

[0050] Mixtures of synthetic and mineral oils can also be used.

[0051] The additional base oils of the lubricating compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins. The polyalphaolefins used as base oils are, for example, obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene, and for which the viscosity at 100°C is between 1.5 and 15 mm2.s 1 according to the ASTM D445 standard. Their average molar mass is generally between 250 and 3000 according to the ASTM D5296 standard. Viscosity index improver additive

[0052] As indicated above, the lubricating composition according to the invention also comprises an additive improving the viscosity index.

[0053] Viscosity index improvers, in particular viscosity index improving polymers, ensure good cold resistance and minimal viscosity at high temperatures. Examples of viscosity index improving polymers include polymer esters, homopolymers or copolymers, hydrogenated or non-hydrogenated styrene, butadiene and isoprene, homopolymers or copolymers of olefin, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA), preferably homopolymers or copolymers of olefin, such as ethylene or propylene.

[0054] According to one embodiment, the viscosity index improving additive is chosen from polymethacrylates (PMA).

[0055] According to a preferred embodiment, the viscosity index improving additive is chosen from comb polymethacrylates.

[0056] According to one embodiment, the content of viscosity index improving additive is from 2% to 15%, preferably from 7% to 12%, preferentially from 9% to 11%, by weight relative to the weight of said lubricating composition. Other additives

[0057] The lubricating composition according to the invention may further comprise one or more additional additives, other than the aforementioned viscosity index improving additive.

[0058] As additional additives, mention may be made of friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, pour point depressant (PPD) additives, dispersants, antifoaming agents, thickeners, corrosion inhibitors, copper passivating agents, emulsifiers, and mixtures thereof.

[0059] Advantageously, a lubricating composition according to the invention comprises one or more additional additives chosen from pour point lowering additives, anti-wear additives, antioxidants and mixtures thereof.

[0060] These additional additives may be added to the base oil mixture according to the invention, in an appropriate quantity, determined by a person skilled in the art. It is understood that the nature and quantity of the additives used are chosen in such a way that the advantageous properties of the lubricating composition are not or are not substantially altered by the envisaged addition.

[0061] A lubricating composition used according to the invention may comprise between 0.01% and 20% by mass, in particular between 0.05% and 15% by mass, of additional additives, in particular as described below, relative to the total mass of the composition.

[0062] Advantageously, a lubricating composition used according to the invention may comprise at least one friction modifying additive. The friction modifying additives make it possible to limit friction by forming monolayers adsorbed on the surfaces of the metals in contact with them. They may be chosen from compounds providing metallic elements and ash-free compounds. Among the compounds providing metallic elements, it is possible cite transition metal complexes such as Mo, Sb. Sn, Fe, Cu, Zn whose ligands may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. Ash-free friction modifying additives are generally of organic origin and may be chosen from fatty acid esters and polyols, distinct from the monoester required according to the invention, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides, fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms. In particular, the molybdenum-based compounds may be chosen from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof.

[0063] Advantageously, a lubricating composition according to the invention may comprise from 0.01% to 5% by mass, preferably from 0.01% to 5% by mass, more particularly from 0.1% to 2% by mass or even more particularly from 0.1% to 1.5% by mass, of friction modifying additives, relative to the total mass of the lubricating composition.

[0064] Preferably, a lubricating composition according to the invention comprises at least one anti-wear additive, an extreme pressure additive or mixtures thereof. The anti-wear additives and the extreme pressure additives are dedicated to protecting the friction surfaces by forming a protective film adsorbed on these surfaces. There is a wide variety of anti-wear additives. Particularly suitable for the lubricating compositions according to the invention are the anti-wear additives chosen from polysulfide additives, sulfur-containing olefin additives or even phospho-sulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OR)(OR'))2, in which R and R', identical or different, independently represent an alkyl group, preferably comprising from 1 to 18 carbon atoms.

[0065] Advantageously, a lubricating composition according to the invention may comprise from 0.01% to 6% by mass, preferably from 0.05% to 4% by mass, more preferably from 0.1% to 2% by mass, of anti-wear additives and extreme pressure additives, relative to the total mass of the composition.

[0066] A lubricating composition according to the invention may also comprise at least one detergent additive. Detergent additives generally make it possible to reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products. The detergent additives that can be used in a lubricating composition according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali or alkaline earth metal. Detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium. These metal salts generally contain the metal in a stoichiometric quantity or in excess, therefore in a quantity greater than the stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in the base oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0067] A lubricating composition according to the invention may comprise from 0.5% to 8%, preferably from 0.5% to 4% by mass, of detergent additive, relative to the total mass of the lubricating composition.

[0068] Advantageously, a lubricating composition according to the invention may comprise at least one antioxidant additive. The antioxidant additive makes it possible to delay the degradation of the lubricating composition in service. This degradation may in particular result in the formation of deposits, the presence of sludge or an increase in the viscosity of the lubricating composition. They act in particular as radical inhibitors or hydroperoxide destroyers.

[0069] Among the commonly used antioxidant additives, mention may be made of phenolic type antioxidants, amine type antioxidant additives, phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, may be ash-generating. The phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0070] Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group. Amino compounds are another class of antioxidant additives that can be used, optionally in combination with the phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example aromatic amines of formula NR5R6R7 in which R5 represents an aliphatic group or an aromatic group, optionally substituted, R6 represents an aromatic group, optionally substituted, R7 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R8S(O)ZR9 in which R8 represents an alkylene group or an alkenylene group, R9 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2. Sulphurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0071] Advantageously, a lubricating composition according to the invention may comprise from 0.1% to 2% by mass, relative to the total weight of the composition, of at least one antioxidant additive.

[0072] Advantageously, a lubricating composition according to the invention may also comprise at least one pour point depressant additive (also called a “PPD” agent for “Pour Point Depressant” in English). By slowing down the formation of paraffin crystals, the pour point depressant additives generally improve the cold behavior of the lubricating composition according to the invention. Examples of pour point reducing agents that may be mentioned are polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

[0073] A lubricating composition according to the invention may comprise from 0.1% to 2%, preferably from 0.2% to 1% by mass of pour point lowering additive(s), relative to the total mass of the composition.

[0074] A lubricating composition according to the invention may also comprise at least one dispersing agent. Such dispersing agents ensure the maintenance in suspension and the evacuation of insoluble solid contaminants constituted by the secondary oxidation products which are formed when the lubricating composition is in service. They may be chosen from Mannich bases, succinimides and their derivatives, such as derivatives of polyisobutylene succinic anhydride.

[0075] In particular, a lubricating composition according to the invention may comprise from 0.2% to 10% by mass of dispersing agent(s), relative to the total mass of the composition.

[0076] A lubricating composition may also comprise at least one antifoam additive, for example chosen from polar polymers such as polymethylsiloxanes or polyacrylates. In particular, a lubricating composition according to the invention may comprise from 0.01% to 3% by mass of antifoam additive(s), relative to the total mass of the lubricating composition.

[0077] It may also comprise at least one anti-corrosion agent or passivating agent of the copper, for example compounds such as polyisobutene succinic anhydrides, thiadiazole sulfonates or mercaptobenzothiazoles. They are typically present in a lubricating composition according to the invention at contents of between 0.01% and 1% by mass, relative to the total mass of the composition.

[0078] The present invention also relates to the use of a lubricating composition as defined above, for lubricating the parts of a motor vehicle engine.

[0079] The present invention also relates to a method for lubricating a motor vehicle engine, in particular a heat engine, comprising bringing at least one part of the engine into contact with a lubricating composition according to the invention.

[0080] The present invention covers all motorized vehicles, preferably comprising at least one combustion engine, in particular heavy vehicles or light vehicles.

[0081] The present invention also relates to the use of a lubricating composition as defined above, for reducing the fuel consumption of a motor vehicle engine.

[0082] The present invention also relates to a method for reducing the fuel consumption of a heat engine, said method comprising a step of lubricating said engine with a lubricating composition as defined above.

[0083] Finally, the present invention also relates to the use of a lubricating composition as defined above, to reduce the carbon footprint of said lubricating composition.

[0084] The invention therefore also relates to the use of a lubricating composition according to the invention to reduce the carbon footprint by reducing fuel consumption, in particular compared to a usual lubricating composition. EXAMPLES

[0085] Example 1: Preparation of lubricating compositions

[0086] The following lubricating compositions (CL compositions according to the invention and CC comparative compositions) are prepared according to methods known to those skilled in the art.

[0087] The compositions are indicated in Table 2 below: CL1 CL2 CCI CC2 CC3 Lubricant Composition Grade OW-16 0W-20 0W-20 0W-20 0W-20 Additive Package 10.1 10.1 10.1 10.1 10.1 Friction Modifier Additive 0.8 0.8 0.8 0.8 0.8 Pour Point Depressant (PPD) 0.2 0.2 0.2 0.2 0.2 Viscosity Index Improver (PMA) 9.2 9.5 9.5 9.2 - First Group IV Oil 7.5 7.5 18 - 8.9 Second Group IV Oil 72.2 71.9 - 79.7 80 Other Group IV Oil - - 61.4 - -

[0088] The first group IV oil in Table 1 has a KV100 equal to 2 mm2 / s.

[0089] The second group IV oil in Table 1 has a KV100 equal to 3.5 mm2 / s and a Noack volatility equal to 11.5%.

[0090] The other group IV oil in Table 1 has a KV100 equal to 4 mm2 / s.

[0091] The additive package notably comprises a dispersant, a detergent, an antioxidant, an anti-wear agent and / or an antifoam agent.

[0092] Example 2: Evaluation of the characteristics of lubricating compositions

[0093] The characteristics of the lubricating compositions are indicated in Table 3 below:

[0094] [Tables3] CL1 CCI CL2 CC2 CC3 KV40 22.66 23.33 22.60 24.43 17.23 KV100 6.811 6.902 6.835 6.972 3.667 HTHS 150°C 2.55 2.40 2.38 2.50 1.52 KV144 3.863 3.892 3.885 3.881 1.916 VI 292 287 295 274 94 Volatility Noack 18.0 27.7 18.0 12.0 18.0 Aft B.42c+7%GO-HTHS 135°C 2.52 2.55 2.54 2.64 1.68 BOV 3.26 3.26 3.26 3.50 3.26

[0095] KV40 (Kinematic Viscosity at 40°C) corresponds to the kinematic viscosity of the lubricating composition at 40°C, measured according to the ASTM D445 standard.

[0096] KV100 (Kinematic Viscosity at 100°C) corresponds to the kinematic viscosity of the lubricating composition at 100°C, measured according to the ASTM D445 standard.

[0097] KV144 (Kinematic Viscosity at 144°C) corresponds to the kinematic viscosity of the lubricating composition at 144°C. This value is calculated from the aforementioned KV40 and KV100 values.

[0098] The VI corresponds to the viscosity index of the lubricating composition, determined according to the ASTM D2270 standard.

[0099] Noack volatility at 250°C is measured according to CEC method L-40-A-93.

[0100] The parameter Aft B.42c+7%GO-HTHS 135°C is measured according to the method described above. In particular, the viscosity calculation is made from the HTHS at 100°C and HTHS at 150°C on the oils after shearing for 42 cycles according to the ASTM D6278-20a standard and dilution with gasoline (SP83) 7%.

[0101] The BOV corresponds to the KV100 viscosity of the base oils of the lubricating composition, measured according to the ASTM D445 standard.

[0102] Table 3 shows that the compositions according to the invention (CL1 and CL2), comprising an additive improving the viscosity index and a mixture of base oils according to the invention, meet the following conditions:

[0103] - KV40 value strictly less than 23.5 mm2 / s;

[0104] - value of KV144 strictly greater than 3.8 mm2 / s;

[0105] - Noack volatility less than 22%; and

[0106] - parameter “Aft B.42c+7%GO-HTHS 135°C” strictly greater than 2.25 mPa.s.

[0107] On the other hand, the comparative composition CCI, which comprises a mixture of base oils different from that according to the invention (with a mixture comprising a first base oil according to the invention but a different second base oil), does not meet the same conditions. Typically, the Noack volatility of CCI is greater than 22%, unlike the compositions according to the invention.

[0108] Similarly, the comparative composition CC2, which does not comprise a mixture of base oils according to the invention (but only a base oil meeting the definition of the second base oil according to the invention), does not fulfil the same conditions. Typically, the KV40 of CC2 is greater than 23.5 mm2 / s, unlike the compositions according to the invention.

[0109] Furthermore, the comparative composition CC3, which comprises a mixture of base oils according to the invention but does not comprise an additive improving the viscosity index, does not meet the same conditions. Typically, the KV144 of CC3 is less than 3.8 mm2 / s, and the parameter “Aft B.42c+7%GO-HTHS 135°C” for CC3 is less than 2.25 mPa.s, unlike the compositions according to the invention.

Claims

Claims

1. Lubricating composition comprising: - a viscosity index improving additive; and - a mixture of at least a first group IV base oil and a second group IV base oil, wherein: . the first group IV base oil has a kinematic viscosity measured at 100°C, according to the ASTM D445 standard, strictly less than 3 mm2 / s, and . the second group IV base oil, different from the first group IV base oil, has a kinematic viscosity measured at 100°C, according to the ASTM D445 standard, less than or equal to 3.5 mmf / s and has a Noack volatility, determined according to the CEC L-40-93 standard, strictly less than 14%.

2. Lubricating composition according to claim 1, of grade XW-Y according to SAE J300 classification, X being equal to 0, 5 or 10 and Y being from 16 to 50, preferably from 16 to 40, in particular equal to 16 or 20.

3. Lubricating composition according to claim 1 or 2, wherein the content of viscosity index improving additive is from 2% to 15%, preferably from 7% to 12%, preferentially from 9% to 11%, by weight relative to the weight of said lubricating composition.

4. Lubricating composition according to any one of the preceding claims, in which the kinematic viscosity measured at 100°C, according to ASTM D445, of the base oil mixture is from 3 to 3.6 mm2 / s, in particular from 3 to 3.5 mm2 / s, preferably from 3.1 to 3.3 mm2 / s.

5. / s. Lubricating composition according to any one of the preceding claims, in which the kinematic viscosity measured at 40°C, according to the ASTM D445 standard of said lubricating composition is between 22 and 23.5 mm2 / s, in particular between 22.5 and 23.5 mm2 / s, preferably between 22.6 and 23 mm2 / s.

6. A lubricating composition according to any preceding claim, wherein the kinematic viscosity at 144°C of said lubricating composition is from 3.8 to 4 mm2 / s, preferably from 3.85 to 3.9 mm2 / s.

7. A lubricating composition according to any preceding claim, wherein the Noack volatility, determined according to CEC L-40-93, of said lubricating composition is from 18% to 22%, preferably 18% to 19%.

8. Lubricating composition according to any one of the preceding claims, in which the viscosity index, determined according to ASTM D2270, is greater than 290, in particular greater than 292.

9. Lubricating composition according to any one of the preceding claims, in which the viscosity index improving additive is chosen from polymethacrylates (PMA), in particular from comb polymethacrylates.

10. A lubricating composition according to any preceding claim, further comprising one or more additives, in particular selected from friction modifying additives, antiwear additives, extreme pressure additives, detergents, antioxidants, pour point depressant (PPD) additives, dispersants, antifoaming agents, thickeners, corrosion inhibitors, copper passivating agents, emulsifiers, and mixtures thereof.

11. Use of a lubricating composition according to any one of the preceding claims, for lubricating the parts of a motor vehicle engine.

12. Use of a lubricating composition according to any one of the preceding claims, for reducing the fuel consumption of a motor vehicle engine.

13. Use of a lubricating composition according to any one of claims 1 to 10, for reducing the carbon footprint of said lubricating composition.