EP2488618A1

EP2488618A1 - Engine lubricant

Info

Publication number: EP2488618A1
Application number: EP10771215A
Authority: EP
Inventors: Jean-Paul Souchez; Alain Bouffet
Original assignee: Total Raffinage Marketing SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2009-10-16
Filing date: 2010-10-15
Publication date: 2012-08-22
Anticipated expiration: 2030-10-15
Also published as: BR112012008947A2; FR2951456B1; BR112012008947B1; EP2488618B1; FR2951456A1; WO2011045773A1

Abstract

The invention relates to the use of an engine oil having kinematic viscosity at 0°C according to standard ASTM D445 of 16 to 27 cSt, including at least one ester (a) of the formula R(OH)m(COOR'(OH)p(OOCR'')q)n for lubricating internal combustion engines of hybrid vehicles, in which the maximum torque, measured between 1000 and 3000 revolutions per minute, is higher than 1000 N.m. The invention also relates to a corresponding lubricant composition.

Description

ENGINE LUBRICANT

Technical area :

The present invention relates to the lubrication of hybrid vehicle engines, particularly heavy-duty vehicles with hybrid engines.

Technical background:

Environmental concerns and the search for savings on fossil fuel resources have led to the development of electric motor vehicles. However, the latter are limited in power, autonomy, and require a very long battery recharging time.

Hybrid drive systems overcome these disadvantages by implementing an electric motor and an internal combustion engine in series or in parallel. A special feature of hybrid systems is the "stop-start" system. The vehicle starts in electric mode, then goes into thermal mode as soon as the speed increases, and vice versa. The engine is stopped at each stop of the vehicle.

Thus, the internal combustion engine of hybrid vehicles undergoes, during its life, a number of stops and starts much higher than in a conventional vehicle. This potentially generates, for the internal combustion engines of hybrid vehicles, specific wear problems, in particular in the long term.

The majority of hybrid vehicles currently in service are passenger light duty vehicles, which operate under light load and are not intended for long-term use (high mileage).

On the other hand, the sustainability problems related to the stop and start system will be particularly sensitive for hybrid heavy-duty vehicles: these vehicles are intended for intensive use and called for high mileage, and their engines operate under heavy load.

This phenomenon will be particularly crucial for heavy-vehicle hybrid vehicles driven mainly in urban areas, for example those intended for deliveries, garbage collection or public transport. It is estimated that an internal combustion engine hybrid bus will experience about 2 million startup during its lifetime, against a few tens of thousands for a classic bus engine, which will solicit much more mechanical parts.

Tests have been carried out on hybrid electric motor / heavy-duty diesel engine systems, simulating the operation of such heavy vehicle vehicles. These tests have shown that the combustion engines undergo a very important wear on the bearings, which completely compromises the operation of the vehicle in service. The optimization of the engine operating cycles, particularly at ramp up ramps, the duration of the engine stops, did not reduce this phenomenon.

On the other hand, it has been found that, in testing, the lowering of the oil temperature from 100 to 40 ° C makes it possible to reduce the wear of the bearings somewhat. This solution, implemented on a test bench is however unrealistic in use, and does not allow anyway to reduce wear to an acceptable level. The tests mentioned above were carried out with engines lubricated with a commercial grade 10W30 engine oil according to the SAE J 300 classification.

WO2008 / 067259 discloses a lubricating composition comprising a base oil and the condensation product of a dicarboxylic acid compound with a dialkoxy or diol substitution, and a C6 to C12 alcohol.

US4820431 discloses a railway diesel engine lubricating composition comprising a base oil, a dispersant, an overbased phenolate, an alkyl sulfonate and a polyhydroxy compound.

US2008 / 090741 discloses a lubricating composition comprising a base oil, an overbased detergent and a weakly basic detergent, with a salt to metal ratio of between 3 and 8.

There is very little prior art on the specific problems of lubrication of hybrid engines. Application GB 2454349 discloses a method of heating the lubricating oil of diesel engines of hybrid vehicles, with the aim of avoiding problems of cold start and loss of power due to friction. This system requires an ancillary device, and goes against the observations made in test.

There is therefore a need for the development of lubricants for reliable operation of internal combustion engines of hybrid-powered heavy-duty vehicles, and in particular likely to reduce wear in said internal combustion engines.

Surprisingly, the Applicant has found that the use in internal combustion engines of heavy-vehicle vehicles equipped with a hybrid system, viscous grade lubricating compositions and including some organic friction modifiers allowed to significantly reduce wear bearings on said motors, which makes possible their commissioning in real conditions.

Summary of the invention

The subject of the present invention is the engine oil and the corresponding use of the kinematic viscosity engine oil at 100 ° C. according to ASTM D445 of between 16 and 27 cSt, comprising at least one ester (a) of formula R (OH) _m (COOR '(OH) _m (OOCR'') _q) "wherein m is an integer from 0 to 4, preferably 0 to 2, n is an integer from 1 to 8, preferably from 1 to 4; m, p and q are integers from 0 to 4, preferably from 0 to 2, and where the sum p + m is strictly greater than zero, with the proviso that if n = 1 then m = 0 and if η > 1, then p = 0 and q = 0,

and wherein R, R 'and R "independently of one another are a linear or branched, saturated or unsaturated hydrocarbon group optionally substituted by one or more aromatic groups, and having 1 to 30 carbon atoms, and / or its borated derivatives for the lubrication of internal combustion engines of vehicles with hybrid engines whose maximum torque, measured between 1000 and 3000 revolutions / minute, is greater than 1000 Nm

Preferably, the ester (a) contains at least one free OH hydroxyl group belonging to the R group, said OH group being located in the alpha, beta or gamma position with respect to the carbon of the CO function of an ester function on which the group R is attached, or contains at least one free hydroxyl OH group belonging to the group R ', said OH group being located in the beta, gamma or delta position with respect to the oxygen of the COO group of an ester function on which the R' group is attached.

Even more preferentially, the R 'group of the ester (a) represents a C ₁ to C ₁₀ , preferably C ₂ to C ₈ , even more preferably C ₃ to C _{6, group} .

According to one embodiment, in the ester (a), n = 1 and the groups R and R "of the ester (a) represent groups Cs to C ₂₅ , preferably C ₁₂ to C ₁₈ .

Preferably, according to this embodiment, at least one ester (a) is chosen from monoesters or diesters of glycerol, even more preferentially chosen from glycerol mono or di oleate, mono or di stearate or mono or di isostearate. glycerol and / or their borated derivatives.

According to another embodiment, n is strictly greater than 1 and the R group of the ester (a) represents a C ₁ -C ₅ , preferably C ₁ -C _{3, group} .

Preferably, according to this embodiment, at least one ester (a) is chosen from citrates, tartrates, malates, lactates, mandelates, glycolates, hydroxypropionates, hydroxyglutarates and / or their borated derivatives.

According to one embodiment, the kinematic viscosity at 100 ° C of the engine oil used according to the invention, measured according to ASTM D445, is between 16.9 and 21.9 cSt.

According to another embodiment, the kinematic viscosity at 100 ° C of the engine oil used according to the invention, measured according to ASTM D445, is between 21.9 and 26.1 cSt. Preferably, the internal combustion engines lubricated according to the invention are diesel engines.

Preferably, the hybrid heavy-vehicle vehicles whose internal combustion engine is lubricated according to the invention, are parallel hybrids.

According to a preferred embodiment, the use of an engine oil according to the invention aims to reduce the wear of internal combustion engines.

Preferably, the use of an oil according to the invention is made on vehicles that operate according to the urban cycle ETC defined by the European Directive 1999/96 / EC.

The subject of the present invention is also a lubricating composition for a hybrid vehicle internal combustion engine of maximum torque greater than 1000 Nm between 1000 and 3000 revolutions minutes, whose kinematic viscosity at 100 ° C. measured according to the ASTM D445 standard is between 16 and 27 cSt, and including:

(a) from 0.5 to 10% by weight of at least one ester of formula R (OH) _m (COOR '(OH) _p ) _n in which m is an integer of 0 to 8, preferably 1 at 4, n is an integer from 1 to 8, preferably from 1 to 4 and p is an integer from 0 to 8, preferably from 1 to 4 and where the sum p + m is strictly greater than zero, R and R 'represent, independently of one another, a linear or branched, saturated or unsaturated hydrocarbon group optionally substituted with one or more aromatic groups and containing from 1 to 30 carbon atoms, and / or its borated derivatives

(c) from 70 to 90% of one or more mineral, synthetic or natural base oils.

Preferably, the lubricating composition according to the invention further comprises:

(b) from 5 to 20% by weight of an additive composition for engine lubricant comprising one or more detergent additives, one or more dispersing additives, one or more antioxidant additives, preferably amino or phenolic additives, one or more antiwear additives, preferentially chosen; among the zinc dithiophosphates.

Detailed description of embodiments

1) Internal combustion engines of hybrid heavy vehicles

The subject of the present invention is the lubrication of the internal combustion engines of heavy goods vehicles equipped with hybrid systems, in particular those intended to circulate mainly in urban areas, such as delivery utilities, garbage trucks or vehicles used for transporting goods. common. The term hybrid vehicle here means vehicles associating an internal combustion engine with an electric motor, preferably the systems where these two motors are associated in parallel, called parallel hybrid vehicles. The operating principle of these vehicles is as follows: • during stationary phases (where the vehicle is stationary), both engines are stopped,

• At start-up, it is the electric motor that ensures the movement of the car, up to higher speeds (25 or 30 km / h),

· When higher speeds are reached, the engine takes over,

• in case of great acceleration, we observe the start of two engines at a time, which allows to have accelerations equivalent to the engine of the same power, or even higher,

· Optionally, during deceleration and braking, kinetic energy is used to recharge the batteries.

Thus, in hybrid vehicles, the internal combustion engine undergoes, during its lifetime, a number of stops and starts much higher than in a conventional vehicle (phenomenon of "stop and start").

In conventional (non-hybrid) engines, wear phenomena are already known to be more severe on heavy goods vehicles than on light vehicles. The trucks operate under heavy load, and the pressure on the pistons is stronger. They also turn at lower revs and support longer the rod bearings. These vehicles are also intended for a long period of use, resulting in greater wear and tear on parts.

In heavy-duty hybrid vehicles, the specific wear associated with the stop and start phenomenon is superimposed on these pre-existing factors, which makes it impossible for their combustion engines to use conventional commercial engine oils used in heavy goods vehicles. .

Heavy-duty vehicles typically have a payload of more than 3.5 tonnes. The engines that equip them are, for both conventional vehicles and for hybrid vehicles, four-stroke engines, most often diesel, which have power characteristics, and especially high torque.

Manufacturers typically characterize their engines by the maximum power developed (ie the maximum or the plateau of the Power curve (in horsepower or kW) vs rpm (revolutions / min or Rad / s)), and by the maximum torque (ie the maximum or the plateau of the Torque curve (in Nm) vs rpm (revolutions / min or Rad / s)).

The heavy-duty engines have a speed of between 800 and 3000 revolutions / min. The maximum or plateau of the power and torque curves is obtained between 1000 and 3000 rpm, most often between 1000 and 1700 rpm. For diesel engines, the maximum torque is generally obtained around 1200 revolutions / minute The present invention relates to the lubrication of internal combustion engines of vehicles with hybrid engines, said internal combustion engines having a maximum torque (measured between 1000 and 3000 rpm), greater than 1000 Nm, preferably greater than 1500, or at 1700, or at 2000 Nm

These motors preferentially develop maximum powers (between 1000 and

3000 revolutions / minute) greater than 300 horses, preferably greater than 320, preferably greater than 350, or 450, or 500, or in the order of 600 horsepower and beyond.

According to a preferred embodiment, said internal combustion engines are diesel engines. Preferentially, vehicles with hybrid powertrain are parallel hybrid vehicles.

The power or torque characteristics referred to herein refer to net power or net torque as defined in SAE J 1349.

The present invention more preferably relates to the lubrication of internal combustion engines of heavy goods vehicles equipped with hybrid systems circulating in an urban environment, where the stop / start phenomenon and the resulting wear are increased.

The urban, peri-urban and motorway operation of heavy-duty engines is characterized in the ETC cycle (European Transient Cycle), also called the "FIGE" cycle, as defined by the European Directive 1999/96 / EC of 13 December 1999. The first part of the cycle (from 0 to 600 s) characterizes urban functioning. This part of the cycle will be referred to as the "ETC Urban Cycle".

2) Base oils or mixture of base oils (c), VI improving polymers

The motor oils used according to the present invention comprise one or more base oils, generally representing at least 70% by weight of said motor oils, and up to 85% or 90% by weight and more.

The base oil (s) used in the engine oils according to the present invention may be oils of mineral or synthetic origin of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized. below, alone or mixed. Saturated content Sulfur content Viscosity index

Group I Mineral oils <90%> 0.03% 80 <VI <120

G r o u p e I I H u i l e s> 90% <0.03% 80 <VI <120

hydrocracked

Group III> 90% <0.03%> 120

Hydrocracked oils or

hydro-isomerized

Group IV PAO Polyalphaolefins

Group V Esters and other bases not included in groups I to IV

These oils may be oils of vegetable, animal or mineral origin. The mineral base oils according to the invention include all types of bases obtained by atmospheric distillation and vacuum of crude oil, followed by refining operations such as solvent extraction, desalphating, solvent dewaxing, hydrotreatment, hydrocracking and hydro iso meris ation, hydro finish.

The base oils of the compositions according to the present invention may also be synthetic oils, such as certain esters of carboxylic acids and alcohols, or polyalphaolefins. The polyoaplphafines used as base oils, for example, are obtained from monomers having from 4 to 32 carbon atoms (for example octene, decene), and a viscosity at 100 ° C of between 1.5 and 15 Cst. Their weight average molecular weight is typically between 250 and 3000.

Mixtures of synthetic and mineral oils may also be employed, for example when formulating multigrade oils to avoid cold start problems.

To formulate multi-grade oils with a viscous grade when hot (grade 50 or 60), it is often also wise to include in the formulation a viscosity index (VI) improving polymer, which makes it possible to guarantee a good cold performance and a minimum viscosity at high temperature, such as, for example, polymeric esters, olefins copolymers (OCP), homopolymers or copolymers of styrene, butadiene or isoprene, polymethacrylates (PMA).

The motor oils according to the present invention may contain from about 0.0 to 20%, or from 5 to 15%, or from 7 to 10% by weight of VI improvers, for example selected from polymeric esters, olefins copolymers (OCP), homopolymers or copolymers of styrene, butadiene or isoprene, polymethacrylates (PMA).

Preferably, the engine oils according to the invention preferably have a viscosity index value or VI, measured according to ASTM D2270 greater than 130, preferably greater than 140, preferably greater than 150.

There is no limitation to the use of any particular base oil (and optionally VI improving polymer) for making the compositions according to the present invention, except that their amount and their nature must be adjusted. to obtain compositions having a viscosity grade sufficiently viscous, that is to say a kinematic viscosity (KV100) at 100 ° C according to ASTM D445, between 16 and 27 cSt. The motor oils according to the invention are preferably grade 50 or 60 according to the SAEJ300 classification, that is to say that their kinematic viscosity at 100 ° C. according to ASTM D445 is preferably between 16.9 and 21.9 cSt or between 21, 9 and 26.1 cSt.

Preferably, the engine oils according to the invention are multigrade oils of 20 W grade, preferably of 15W grade according to the SAEJ classification, ie their dynamic viscosity (CCS) according to ASTM D5293 is less than 9500 mPa.s. at -15 ° C, preferably below 7000 mPa.s at -20 ° C.

3) Hydroxyl esters (a)

The motor oils used in the invention comprise at least one hydroxyl ester (a) of formula

R (OH) _m (COOR '(OH) _p (OOCR ") _q ) _n

wherein m is an integer of 0 to 4, preferably 0 to 2, n is an integer of 1 to 8, preferably 1 to 4; m, p and q are integers from 0 to 4, preferably from 0 to 2, and where the sum p + m is strictly greater than zero, with the proviso that if n = 1 then m = 0 and if η > 1, then p = 0 and q = 0,

and wherein R, R 'and R "independently of one another are a linear or branched, saturated or unsaturated hydrocarbon group optionally substituted by one or more aromatic groups, and having 1 to 30 carbon atoms, and / or its According to a preferred embodiment, the ester (a) contains at least one free OH hydroxyl group belonging to the R group, said OH group being located at the alpha, beta or gamma position with respect to the carbon of the CO 2 function. an ester function to which the group R is attached, or contains at least one free OH hydroxyl group belonging to the group R ', said OH group being located in the beta, gamma or delta position with respect to the oxygen of the COO group of a ester function on which the group R 'is attached. Preferably R 'represents a C ₁ -C ₁₀ , preferably C ₂ -C ₆ , even more preferentially C ₃ -C _{6, group} .

According to one embodiment, n is equal to 1 and R and R "represent C ₆ to C ₆ groups, preferably C ₁₂ to C 18 groups. When R and / or R" are saturated, more stable compounds are obtained. oxidation. The presence of unsaturation leads to liquid compounds at room temperature, which are more easily solubilized in the oils.

Preferably, according to this embodiment, the hydroxylated esters (a) may be chosen from monoesters or diesters obtained from glycerol, such as glycerol mono or di oleate, mono- or di-stearate or glycerol mono or di isostearate. , and their borated derivatives.

According to another embodiment n is an integer strictly greater than 1 and the R group of the ester (c) represents a group -C 5, preferably C l -C _3.

Preferentially, according to this embodiment, the hydroxylated esters (a) may also be chosen from citrates, tartrates, malates, lactates, mandelates, glycolates, hydroxypropionates, hydroxyglutarates or their borated derivatives.

The esters of formula R (OH) _m (COOR '(OH) _p (OOCR ") _q ) _n according to the invention are prepared according to methods known to those skilled in the art, in particular by reaction of a polycarboxylic acid of formula R (OH) _m (COOH) _n with an alcohol of formula R '(OH) or a polyol of formula R' (OH) _p with monocarboxylic acids RCOOH and / or R'COOH, the substituents R, R ', R and the indices m, n, p being as defined above.

The oils used according to the invention may comprise between 0.5 and 10% by weight, preferably between 1 and 7% by weight, or between 2 and 5% by weight of such esters (a).

Surprisingly, the applicant has demonstrated that the use of these compounds in a viscous grade motor oil (grade SAE 50 and 60 for example), can significantly reduce the wear bearings or rod bearing on the Hybrid heavy-duty engines, which are, with conventional grade 30 oils, at a level that does not allow the reliable operation of the engine. The wear of the dispensing members is also reduced.

It is known that the bearings operate in hydrobdynamic lubrication regime (complete oil film). The use of viscous grade motor oils has the effect of increasing the thickness of the oil film, which helps to maintain this lubrication regime, even under severe operating conditions.

The additional protective effect observed by the use of organic friction modifiers in the oils according to the invention is all the more surprising since these compounds, which form adsorptive layers structured on the surface of the parts, are known to act essentially in mixed or limited lubrication regime.

It should also be noted that the level of antiwear additive oils used according to the invention may be identical to that of conventional oils for internal combustion engine heavy vehicles.

4) Other additives

The engine oils used according to the invention may further contain any type of additives suitable for use as engine oil, particularly heavy-duty engine. These additives may be introduced individually and / or included in packages of additives used in commercial four-stroke engine lubricant formulations, with performance levels as defined by ACEA (Association of European Automobile Manufacturers) and / or ΑΡΙ (American Petroleum Institute), for example respectively ACEA E9 and API CJ-4 well known to those skilled in the art. These additive packages (or additive compositions) are concentrates comprising about 30% by weight of dilution base oil.

Thus, the compositions according to the invention may contain, in particular and without limitation, anti-wear and extreme pressure additives, antioxidants, overbased or non-overbased detergents, pour point improvers, dispersants, antifoam, thickeners. ..

The anti-wear and extreme pressure additives protect the friction surfaces by forming a protective film adsorbed on these surfaces. The most commonly used is Zinc di thiophosphate or DTPZn. This category also contains various phosphorus, sulfur, nitrogen, chlorine and boron compounds.

There is a wide variety of anti-wear additives, but the most used category in motor oils is that of phospho-sulfur-containing additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or DTPZn. Preferred compounds are of formula

Zn ((SP (S) (OR1) (OR2)) 2, where R1 and R2 are alkyl groups, preferably containing from 1 to 18 carbon atoms, DTPZn is typically present at levels of the order of 0, 1 to 2% by weight in the motor oils.

Phosphates of amines, polysulfides, especially sulfur-containing olefins, are also commonly used anti-wear additives.

The anti-wear and extreme pressure additives are generally present in the compositions for heavy-duty engine lubricants at contents of between 0.5 and 6%, preferably between 0.7 and 2%, preferably between 1 and 1.5% by weight. . Antioxidants delay the degradation of oils in service, which can result in the formation of deposits, the presence of sludge, or an increase in the viscosity of the oil. They act as free radical inhibitors or destroyers of hydroperoxides. Among the antioxidants commonly used are the antioxidants of the phenolic type, amines.

Phenolic anoxidants may be ashless, or may be in the form of neutral or basic metal salts. Typically, they are compounds containing a sterically hindered hydroxyl group, for example when 2 hydroxyl groups are in the o or p position of each other, or when the phenol is substituted with an alkyl group containing at least 6 carbon atoms. .

Amino compounds are another class of antioxidants that can be used alone or possibly in combination with phenolics. Typical examples are aromatic amines, of formula R ₈ R ₉ R ₁₀ N, where R 5 is an aliphatic group, or an optionally substituted aromatic group, R ₉ is an optionally substituted aromatic group, Rio is hydrogen, or a group alkyl or aryl, or a group of formula RnS (O) _x R12, where R11 is alkylene, alkenylene, or aralkylene, and x is 0, 1 or 2.

Sulfurized alkyl phenols or their alkali and alkaline earth metal salts are also used as antioxidants.

Another class of antioxidants is that of oil-soluble copper compounds, for example copper thio or dithiophosphate, copper and carboxylic acid salts, copper dithiocarbamates, sulphonates, phenates, acetylacetonates. Copper salts I and II, succinic acid or anhydride are used.

These compounds, alone or as a mixture, are typically present in lubricating compositions for engine weight lords in amounts of between 0.1 and 5% by weight, preferably between 0.3 and 2% by weight, even more preferably between 0, 5 and 1.5% by weight.

Detergents reduce the formation of deposits on the surface of metal parts by dissolving the secondary products of oxidation and combustion, and allow the neutralization of certain acidic impurities from combustion and found in the oil.

The detergents commonly used in the formulation of lubricating compositions are typically anionic compounds having a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation is typically a metal cation of an alkali or alkaline earth metal.

The detergents are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulphonates, salicylates and naphthenates, as well as the salts of phenates, preferably of calcium, magnesium, sodium or barium. These metal salts may contain the metal in an approximately stoichiometric amount or in excess (in an amount greater than the stoichiometric amount). In the latter case, we are dealing with so-called overbased detergents.

The excess metal providing the overbased detergent character is in the form of oil-insoluble metal salts, for example carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate, preferably calcium, magnesium, sodium or barium.

The lubricant compositions according to the present invention may contain any type of detergent known to those skilled in the art, neutral or overbased. The more or less overbased character of the detergents is characterized by the BN (base number), measured according to the ASTM D2896 standard, and expressed in mg of KOH per gram. Neutral detergents have a BN between about 0 and 80. The overbased detergents, they BN values typically of the order of 150 and more, or 250 or 450 or more. The BN of the lubricant composition containing detergents is measured by ASTM D2896 and expressed as mg KOH per gram of lubricant.

Preferably, the amounts of detergents included in the motor oils according to the invention are adjusted so that the BN of said oils, measured according to ASTM D2896, is between 5 and less than or equal to 20 mg of KOH per gram of d motor oil, preferably between 8 and 15 mg of KOH per gram of engine oil

Pour point depressant additives improve the cold behavior of oils by slowing the formation of paraffin crystals. They are for example alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylsphenols, polyalkylnaphthalenes, alkylated polystyrene, etc. They are generally present in the oils according to the invention at contents of between 0.1 and 0.5% by weight. .

Dispersants, for example succinimides, PIB (polyisobutene) succinimides,

Mannich bases ensure the suspension and evacuation of insoluble solid contaminants consisting of secondary oxidation products that are formed when the engine oil is in use. The dispersant level is typically relatively higher in heavy-duty engine oils than in light-duty engine oils, mainly due to longer oil change intervals. It is typically between 4 and 10% by weight, preferably between 4.5 and 7% by weight.

Examples

The operation of a hybrid system was simulated by a test consisting of a succession of 500 hours (15000 cycles) of:

- starts Operation with alternating acceleration and deceleration

slow descent

5 seconds slow motion

stop

The system tested includes a 6-cylinder diesel engine with a maximum torque of 1200 Nm from 1200 to 1700 rpm. It is a hybrid type parallel and includes a starter alterno between the clutch and the gearbox of the vehicle. The engine oil is around 100 ° C in these tests. The wear is followed by a usual technique of radiotracers, consisting of irradiating the surface of the bearings whose wear is to be tested, and measuring at the end of the test the radioactivity of the engine oil, which contains proportionally irradiated metal particles. to wear the parts in question.

Oil A is a 10W30 heavy duty commercial grade engine oil formulated with an ACE A E9 performance lighter engine oil additive package. Oils B and C contain the same additivation but are of grade respectively 15W50 and 20W50. The oil D is an oil according to the invention, which also contains the same additivation and is grade 15W50.

The mass compositions and properties of the oils tested are grouped in the table below:

off base oil dilution additive package The additive package is identical for oils A, B, C and D: it is a classic package for diesel engine oils (ACEA E9 performance level), including:

dispersants

detergents

Antioxidants

zinc dithiophosphate antiperspirants (ZnDDPs).

It should be noted that no additional antiwear has been added in the oil D according to the invention. The antiwear rate of the D oils is identical (slightly lower) than that of the reference.

Tests with the reference oil A showed a high wear rate, corroborated by visual observations (wear on 40% of the surface of the first bearing).

The use of viscous grade (grade SAE 50) for oils B and C reduced bearing wear by 25% compared to the reference, and the introduction of friction modifiers in oil D The invention has allowed an additional 17% lowering. The wear of the distribution members such as the cams is also reduced by 50% with the oil D.

Claims

A lubricating composition, whose kinematic viscosity at 100 ° C measured according to ASTM D445 is between 16 and 27 cSt, and comprising:

(a) from 0.5 to 10% by weight of at least one ester of formula

R (OH) _m (COOR '(OH) _p ) _n

in which

m is an integer of 0 to 8, preferably 1 to 4,

n is an integer of 1 to 8, preferably 1 to 4

p is an integer of 0 to 8, preferably 1 to 4

and where the sum p + m is strictly greater than zero,

R and R 'represent, independently of each other, a saturated or unsaturated, linear or branched hydrocarbon group, optionally substituted with one or more aromatic groups, and comprising from 1 to 30 carbon atoms, and / or its borated derivatives

(b) from 70 to 90% of one or more mineral, synthetic or natural base oils.

The lubricating composition of claim 1 further comprising

(c) from 5 to 20% by weight of an additive composition for motor lubricant comprising one or more detergent additives, one or more dispersant additives, one or more antioxidant additives, preferably amino or phenolic additives, one or more antiwear additives, preferentially chosen; among the zinc dithiophosphates.

3. Motor oil, kinematic viscosity at 100 ° C according to ASTM D445 between 16 and 27 cSt, comprising at least one ester (a) of formula

R (OH) _m (COOR '(OH) _p (OOCR ") _q )"

in which

m is an integer of 0 to 4, preferably 0 to 2,

n is an integer of 1 to 8, preferably 1 to 4;

m, p and q are integers from 0 to 4, preferably from 0 to 2, and where the sum p + m is strictly greater than zero, with the proviso that if n = 1 then m = 0 and if n > l, then p = 0 and q = 0,

and wherein R, R 'and R "independently of one another are a linear or branched, saturated or unsaturated hydrocarbon group optionally substituted by one or more aromatic groups, and having 1 to 30 carbon atoms, and / or its borated derivatives.

4. The oil or composition according to one of claims 1 to 3 wherein the ester (a) contains at least one free OH hydroxyl group belonging to the R group, said OH group located in the alpha, beta or gamma position relative to the carbon of the CO function of an ester function to which the group R is attached, or contains at least one free OH hydroxyl group belonging to the group R ', said OH group being located in a beta, gamma or delta position with respect to oxygen of the COO group of an ester function to which the R 'group is attached.

5. Oil or composition according to one of claims 1 to 4 wherein the group R 'of the ester (a) represents a group to C ₁₀ and preferably C ₂ -C _8, even more preferably C ₃ at C ₆ .

6. The oil or composition according to one of claims 1 to 5 wherein n = 1 and the groups R and R "of the ester (a) are Cs to C _{25 groups} preferably C ₁₂ to C ₁₈ .

7. The oil or composition according to claim 6, wherein at least one ester (a) is chosen from monoesters or diesters of glycerol, preferably chosen from glycerol mono or di oleate, mono or di stearate or mono or di glycerol isostearate and / or their borated derivatives.

8. Oil or composition according to one of claims 1 to 5 wherein n is strictly greater than 1 and the R group of the ester (a) is a group Ci-C ₅ , preferably Ci-C ₃ .

An oil or composition according to claim 8 wherein at least one ester (a) is selected from citrates, tartrates, malates, lactates, mandelates, glycolates, hydroxypropionates, hydroxyglutarates and / or their borated derivatives.

An oil or composition according to one of claims 1 to 9 wherein the kinematic viscosity at 100 ° C of the engine oil, measured according to ASTM D445, is between 16.9 and 21.9 cSt.

An oil or composition according to one of claims 1 to 9 wherein the kinematic viscosity at 100 ° C of the engine oil, measured according to ASTM D445, is between 21.9 and 26.1 cSt.

12. Use of an oil or composition according to one of claims 1 to 1 1 for the lubrication of a hybrid vehicle internal combustion engine of maximum torque greater than 1000 N.m between 1000 and 3000 revolutions minutes.

13. Use according to claim 12 wherein the internal combustion engines are diesel engines.

The use of claim 12 or 13 wherein the hybrid HGVs are parallel hybrids.

15. Use according to one of claims 12 to 14 for reducing the wear of internal combustion engines.

16. Use according to one of claims 12 to 15 wherein the vehicles operate according to the urban cycle ETC defined by the European Directive 1999/96 / EC.