AU2009241948B2

AU2009241948B2 - Multipurpose lubricating fluid

Info

Publication number: AU2009241948B2
Application number: AU2009241948A
Authority: AU
Inventors: Bernard-Victor Lamy; Jean-Paul Souchez
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2008-04-11
Filing date: 2009-04-08
Publication date: 2014-05-29
Anticipated expiration: 2029-04-08
Also published as: AU2009241948A1; AR071192A1; EP2334772A1; BRPI0910604A2; BRPI0910604B1; WO2009125075A1; WO2009133292A1; MX2010011187A

Abstract

The present invention relates to multipurpose lubricating fluids usable in different automotive vehicle parts, particularly in the engine, transmission, or hydraulic circuit, and relates to a lubricating composition containing at least one base oil from groups I through II and a mixture of at least two polymers having a difference in permanent shear stability index (PSSI), measured from at least 25 after a 20-hour standardized KRL test at 100°C, and having a viscosity profile such as: (a’) at 100°C before shearing, the kinematic viscosity of the novel lubricating composition is greater than 15.0 cSt, preferably 15.5 cSt, and less than 16.3 cSt; (a) at 100°C after a 30 cycle Bosch test according to the CEC-L-14-A-93 standard, the final kinematic viscosity of the lubricating composition is greater than 12.0 cSt, preferably within the range of 12.0 to 15.0 cSt, for an oil starting at grade 40; (b) at 100°C after a 20-hour KRL test according to the CEC-L-45-A-99 standard, the viscosity of the lubricating composition is greater than 10.0, preferably within the range of 10.0 to 12.5 cSt, for an oil starting at grade 40; and (c) at 40°C after a 3-hour KRL test according to the CEC-L-45-A-99 standard the duration of which is reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil starting at grade 40.

Description

MULTIFUNCTIONAL LUBRICATING FLUID Field of the invention 5 The present invention relates to multifunctional lubricating fluids for use in the various mechanisms of motor vehicles, in particular in the engine, the transmission or the hydraulic circuit. More precisely, the invention relates to a single fluid that can be used directly in several types of applications, in particular in the various mechanisms of motor vehicles such as engines, transmission devices (gearboxes and transfer 10 boxes), hydraulic circuits and other ancillary mechanisms without any need for modification; in other words, the composition of this fluid is directly suitable for the various types of use in question. Background of the invention At present every motor vehicle uses a variety of monofunctional lubricating fluids, 15 each fulfilling different functions, for example engine oils, gearbox oils, hydraulic oils etc. The formulation of a monofunctional oil consists conventionally of a mixture of mineral, semi-synthetic or synthetic base oils, a package of performance additives, and optionally a viscosity improving polymer and a pour point improver. 20 When a monofunctional lubricating oil is in service in a mechanism, the constant shear to which the viscosity improving polymer is subjected leads to a decrease in viscosity of the oil. The extent and rate of this decrease in viscosity depend on the nature and amount of viscosity improving polymer used. Now, the shear rates to which the lubricant is subjected differ from one 25 mechanism to another. For example, the high-pressure hydraulic circuits operating the lifting mechanisms produce more shear than the gearboxes, and they in turn produce more shear than the engines. If a monofunctional oil is used in a mechanism other than that for which it has been formulated, its viscosity may move away from the value required for optimum 30 functioning of said mechanism. Formulations of multifunctional oils for engine, gearbox and hydraulic circuit are already marketed under the names TOTAL Multi TP, FINA Penta, ELF Noria. Their 2424890_1 (GHMatters) 2 design is based on an appropriate choice of viscosity improving polymer and the amount incorporated. The varying level of shear stability of the viscosity improving polymer incorporated in these multifunctional oils for engine, gearbox and hydraulic circuit 5 will determine the respective levels of viscosity attained by this oil in each mechanism. If we use a viscosity improving polymer that is very sensitive to shear, the viscosity will drop very rapidly, even in those mechanisms having a low shear rate: it will drop below the minimum viscosities required in the engine and the gearbox. 10 Conversely, if we use a polymer with a very high shear stability, the viscosity will remain high for a very long time even in those mechanisms having a high shear rate: it will take a very long time before the viscosity reaches in the best case a low enough value, as required for example in the hydraulic circuits. This can cause persistent cold starting problems for the lifting mechanisms operated by the hydraulic circuit. 15 If the behaviour of the polymer is intermediate, the adjustment parameters allowing simultaneous fulfilment of the 3 constraints of minimum viscosities in engine and gearbox, and maximum viscosity in the hydraulic system, are the amount and nature of the viscosity improving polymer used. Most of the multifunctional oils currently in use are based on this principle. We 20 therefore end up with compromises that exceed the limits of capacity for use of the existing multifunctional oils in three mechanisms at the same time. Thus, the existing formulations of multifunctional oils do not allow them to simultaneously reach the performance levels expected in the various target mechanisms. Moreover, the performance levels are also not achieved in particular 25 with respect to the high-temperature stability in the engines and the transmission and the cold starting of the hydraulics. There is therefore a need for a single fluid whose performance is suitable for lubricating various mechanisms of a vehicle at the same time. In particular, there is a need for a single fluid that can be used for all three applications: engine, transmission 30 and hydraulic circuit. There is also a need for the performance of this same single fluid to be adapted for good high-temperature stability in the engine and transmission and for cold starting of the hydraulics. In particular, in hot countries, oil can be subject to severe thermal stresses. 2424890_1 (GHMatters) 3 New oil must therefore have a high kinematic viscosity, in order to resist high external temperatures and retain sufficient viscosity after shear in the engine and the gearbox, while remaining sufficiently fluid to be acceptable in the hydraulic circuit. Moreover, in order to have economically viable solutions available in these same 5 countries the use of formulations based on bases of groups I and II is preferred. Given their low viscosity index, typically less than 110, it is impossible to formulate multifunctional oils according to the concepts of the prior art, i.e. by addition of a polymer improving the VI index, from bases of group I and/or II. There is therefore a need for multifunctional oils suitable for the requirements of 10 hot countries and formulated from oils of group I and/or group II. Having a single fluid available for lubricating various mechanisms of a vehicle, relative to the use of several monofunctional oils, offers advantages in particular in terms of ease of maintenance and storage, servicing of the vehicle or of a fleet of vehicles, packaging and logistics. 15 This is true in particular for the large fleets of public service vehicles, which are often used on isolated sites and are subject to severe weather conditions, without adequate storage equipment. Summary of the invention Thus, the invention provides a lubricating composition comprising at least one 20 base oil of groups I to II and a mixture of at least two polymers having a difference in permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at I 00*C of at least 25, and having a viscosity profile such that: (a') at 100*C, before shear, the kinematic viscosity of the new lubricating composition is greater than 15.0 cSt, preferably 15.5 cSt, and less than 16.3 cSt, 25 (a) at 100*C after the Bosch-30 cycles test according to standard CEC-L-14-A-93 the kinematic viscosity of the final lubricating composition is greater than 12.0 cSt, preferably in the range from 12.0 to 15.0 cSt for an oil initially of grade 40, and (b) at 100*C after the KRL-20 hours test according to standard CEC-L-45-A-99 the viscosity of the lubricating composition is greater than 10.0, preferably in the 30 range from 10.0 to 12.5 for an oil initially of grade 40, and (c) at 40*C after the KRL-3 hours test, according to standard CEC-L-45-A-99 with the test duration reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 40. 242480_1 (GHMfters) 4 Or also, the invention provides a lubricating composition comprising at least one base oil of groups I to II and a mixture of at least two polymers having a difference in permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 1 00 0 C of at least 25, and having a viscosity profile such that: 5 (a') at 100*C, before shear, the kinematic viscosity of the new lubricating composition is greater than 16.3 cSt and less than 21.9 cSt, (a) at 100*C after the Bosch-30 cycles test according to standard CEC-L-14-A-93 the kinematic viscosity of the final lubricating composition is greater than 15.0 cSt, preferably in the range from 15.0 to 20.0 cSt for an oil initially of grade 50, 10 (b) at 100*C after the KRL-20 hours test according to standard CEC-L-45-A-99 the viscosity of the lubricating composition is greater than 10.0 cSt and strictly less than 11.0 cSt, preferably less than or equal to 10.9 cSt for an oil initially of grade 50, and (c) at 40*C after the KRL-3 hours test, according to standard CEC-L-45-A-99 with 15 the test duration reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 50. This formulation of multifunctional lubricant can be used for simultaneously lubricating various mechanisms of a motor vehicle. More particularly, this single lubricant is used for simultaneously lubricating at least three mechanisms, namely the 20 engine, the gearbox and the hydraulic circuit, as it offers a viscosity profile adapted to the conditions of use required in each target mechanism. For simultaneously lubricating the various target mechanisms of a motor vehicle, this single lubricant incorporates a mixture of polymers having different shear stabilities. 25 The nature and the respective amount of the different types of polymers are determined in such a way that the lubricating composition incorporating this mixture adapts very rapidly to the conditions of use required in each target mechanism, owing to its viscosity profile. Thus, the lubricating composition includes at least 50 wt.%, based on the weight 30 of the final composition, of one or more base oils including at least one oil selected from the oils of groups I to II and at least 5%, preferably from 5 to 40%, or more preferably 5 to 15 wt.% based on the weight of the final composition, of a mixture comprising at least two different polymers of type "A", "B", or "C", each of the 2424890_1 (GHMatters) 5 polymers of the mixture differing from one another in that they belong to a separate range of permanent shear stability index (PSSI) such that: -the polymers of type "A" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at I 00*C, less than or equal to 40, 5 -the polymers of type "B" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100*C, between 40 and 65 exclusive; -the polymers of type "C" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 1 00*C, greater than or equal to 10 65; said composition in which at least two polymers have a difference in PSSI measured after the standardized KRL 20 hours test at 1 00*C, of at least 25. Preferably, the lubricating composition comprises at least 50%, preferably at least 70 wt.%, of one or more base oils selected from the oils of groups I to II. 15 According to an embodiment, each of the polymers of the mixture is obtained from monomer units of a different chemical nature. According to another embodiment, each polymer of the mixture is obtained from monomer units of identical chemical nature, and the polymers of the mixture differ from one another in that they belong to a different range of permanent shear stability 20 index (PSSI) measured after the standardized KRL 20 hours test at 100*C and by at least one physicochemical characteristic selected from the number-average or weight average molecular weight, the molecular weight distribution of said polymer characterized by the polydispersity index, the morphology of the three-dimensional network of said polymer characterized by its degree of crosslinking and/or branching. 25 According to an embodiment, the mixture comprises at least two polymers, the amount of one polymer relative to the total weight of the polymer mixture ranging from 10% to 90%. According to an embodiment, the mixture comprises two polymers, one of type A and the other of type C, wherein, preferably, the weight ratio of the mixture of the two 30 polymers A/C ranges from 10/90 to 90/10. According to an embodiment, the lubricating composition according to the invention additionally comprises from 5 to 30 wt.%, relative to the weight of the final composition, of a package of functional additives and optionally less than I wt.%, 242489_1 (GHKaters) 6 preferably from 0.2% to 0.5 wt.%, relative to the weight of the final composition, of a pour point improver. According to an embodiment, the polymers of the mixture are selected from polymers of the viscosity improver type, also called viscosity index improving or VI 5 improving polymers, and optionally from polymers of the pour point improver type. Preferably, the viscosity improving polymers are selected from poly-alpha-olefins (PAO) with a kinematic viscosity at I 00*C greater than 90 cSt, poly-isobutenes (PIB), polymeric esters, olefin copolymers (OCP), homopolymers or copolymers of styrene, of butadiene or of isoprene, polymethacrylates (PMAs). 10 Preferably, the pour point improving polymers are selected from polymethacrylates (PMAs). Preferably, the polymers of type A are viscosity improving polymers selected from polymethacrylates, poly-alpha-olefins with a kinematic viscosity at 100*C greater than 90 cSt, polyisobutenes, polymeric esters. 15 Preferably, the polymers of type C are viscosity improving polymers selected from polymethacrylates, olefinic copolymers, hydrogenated styrene-isoprene copolymers, copolymeric esters. Preferably, the polymers of type B are viscosity improving polymers of the polymethacrylate type. 20 According to another aspect the invention relates to a method of making a lubricating composition according to the invention wherein a mixture comprising at least two different polymers is incorporated in at least one oil of groups I to II optionally comprising a package of additives and optionally a pour point improver. According to an embodiment, at least one of the polymers of the mixture is a 25 viscosity improver, which is incorporated directly in the composition as a separate compound, independently of the package of additives. According to another embodiment of the method, all or part of at least one of the viscosity improving polymers of the mixture is incorporated in the composition as an element of the package of additives. 30 According to another embodiment of the method, all or part of at least one of the viscosity improving polymers of the mixture is incorporated in the composition in the form of a diluent of the package of additives. 242480_1 (GHMaters) 7 According to another aspect the invention relates to the use of a lubricating composition according to the invention as a single fluid for lubricating various mechanisms of motor vehicles. Preferably, the single fluid is used for lubricating at least three mechanisms of 5 motor vehicles, the engine, the gearbox and the hydraulic system of the vehicle. More preferably, the single fluid is also used for lubricating the circuit for operating the brakes, the on-board compressor and optionally other ancillary mechanisms. Detailed description of the embodiments of the invention 10 (A) Determination of shear stability: The shear stability of a compound in an oil is characterized by the PSSI (Permanent Shear Stability Index), defined in standard ASTM-D6022-06 and calculated from the kinematic viscosities of said compound in the oil before and after a defined shearing process. 15 The formula for the PSSI of a polymer in an oil is given by: PSSI = 100 x (Vi - Vc)/(Vi - Vo), where: - Vi = initial viscosity before shear of the oil + polymer mixture at 100*C. - Vc = viscosity of the oil + polymer mixture after a shearing process at 100C. 20 - Vo = initial viscosity before shear of the oil alone at 100*C. Thus, the higher the PSSI of a polymer in the reference oil, the more said polymer is said to be sensitive to shear. The shearing process selected for determining the PSSI of the polymers according to the present invention is the KRL 20 hours test, according to standard CEC-L-45-A 25 99. The reference oil selected for measuring the PSSI of the polymers according to the present invention is a base oil from group I (according to the API classification) with a viscosity of 3.53 cSt at 100 C. Hereinafter, and unless otherwise stated, the PSSI of a polymer will be the PSSI 30 measured according to standard ASTM-D6022-06, measured in a diluent oil of group I (according to the API classification and with a viscosity of 3.53 cSt at 100*C, after the KRL 20 hours test, according to standard CEC-L-45-A-99). 2424890_1 (GHMatters) 8 In order to determine the composition of the mixtures of polymers incorporated in the lubricants according to the present invention, the applicant has defined the shearing conditions representative of each of the mechanisms considered and the levels of viscosity appropriate to each mechanism. 5 (B) Determination of the viscosity profile 1. Conditions of use as engine oil: For engine lubricants, the CEC-L-14-A-93 (or ASTM D6278) standard defines the test representative of the shearing conditions in the engine, known as the Bosch-30 cycles test. 10 The SAE J 300 classification defines the viscosity grades of new engine oils in particular by measurement of their kinematic viscosities at 40*C and/or I 00*C. An engine oil is of grade 40 according to SAE J 300 if its kinematic viscosity at 100*C is from 12.5 to 16.3 cSt. An engine oil is of grade 50 according to SAE J 300 if its kinematic viscosity at 15 100*C is from 16.3 to 21.9 cSt. The engine oils of grade 40, in particular the most viscous of them (and preferably those with a viscosity greater than 15.0 cSt, preferably 15.5 cSt) or of grade 50 are generally used in hot climates. As for the ACEA standards, they define in detail a certain number of 20 supplementary specifications for engine oils, and in particular stipulate the maintaining of a certain level of viscosity for oils subjected in operation to shear in the engine. Thus, according to ACEA series E2 or E3 the kinematic viscosity of engine oils of grade 40 and 50, measured at 100*C, after the Bosch-30 cycles test, must be greater 25 than 12.0 and 15.0 cSt, respectively. The lubricants according to the present invention that are usable as engine lubricants have a kinematic viscosity at 100'C greater than 12.0 cSt, preferably in the range from 12.0 to 15.0 cSt after the Bosch-30 cycles test according to the CEC-L-14 A-93 standard for an oil initially of grade 40. 30 After this same test, these lubricants have a kinematic viscosity at 1 00*C which is greater than 15.0 cSt, preferably in the range from 15.0 to 20.0 cSt for an oil initially of grade 50. 2424890_1 (GHMattes*) 9 The terms oil "initially of grade 40" or "initially of grade 50" are used to designate an oil which satisfies the conditions defined by the classification SAE J 300 for grade 40 or grade 50 respectively, when it is fresh, i.e. before use, i.e. before having been subjected to any shear in the mechanism of the vehicle in which it will be put into 5 service and before having been subjected to shear under standardized test conditions. 2. Conditions of use as gearbox oil: For gearbox lubricants, the CEC-L-45-A-99 standard defines the test representative of the shearing conditions in the gearbox, known as the KRL 20 hours test. 10 The applicant determined, from the data of tests for monitoring oils in service, that a viscosity of a lubricant at 100*C after the standardized KRL 20 hours test greater than 10.0 cSt, preferably in the range from 10.0 to 12.5 cSt, for an oil initially of grade 40 was suitable for use in gearboxes in a hot climate. Similarly, a viscosity of a lubricant at I 00*C after the standardized KRL 20 hours 15 test greater than 10.0 cSt and strictly less than 11.0 cSt, preferably less than or equal to 10.9 cSt, for an oil initially of grade 50 is suitable for use in gearboxes in a hot climate. 3. Conditions of use as hydraulic circuit oil: The applicant also determined that the shearing conditions to which a lubricant is 20 subjected in a hydraulic circuit could be represented by the KRL test according to the CEC-L-45-A-99 standard. The applicant noticed that for operation in the hydraulic circuit while avoiding the problem of starting with new oil, in particular at low temperature, the viscosity of the lubricant, measured at 40*C, should be less than 75 cSt for hot climates after the KRL 25 test according to the CEC-L-45-A-99 standard, the duration of which is reduced from 20 hours to 3 hours, for an oil initially of grade 40 or 50. Thus, the lubricating compositions according to the present invention are suitable simultaneously for use in engines, gearboxes, and hydraulic circuits, as they have a viscosity profile which meets the cumulative conditions below: 30 For an oil initially of grade 40: (a') at 100*C, before shear, the kinematic viscosity of the new lubricating composition is greater than 15.0 cSt, preferably 15.5 cSt and less than 16.3 cSt, 2424890_1 (GHMattems) 10 (a) at 100*C after the Bosch-30 cycles test according to the CEC-L-14-A-93 standard the kinematic viscosity of the final lubricating composition is greater than 12.0 cSt, preferably in the range from 12.0 to 15.0 cSt for an oil initially of grade 40, (b) at 100*C after the KRL 20 hours test according to the CEC-L-45-A-99 5 standard the viscosity of the lubricating composition is greater than 10.0, preferably in the range from 10.0 to 12.5 for an oil initially of grade 40, and (c) at 40*C after the KRL 3 hours test, according to the CEC-L-45-A-99 standard, the test duration of which is reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 40. 10 For an oil initially of grade 50: (a') at 100*C, before shear, the kinematic viscosity of the new lubricating composition is greater than 16.3 cSt, and less than 21.9 cSt, (a) at 100*C after the Bosch-30 cycles test according to the CEC-L-14-A-93 standard the kinematic viscosity of the final lubricating composition is greater than 15 15.0 cSt, preferably in the range from 15.0 to 20.0 cSt for an oil initially of grade 50, (b) at 100*C after the KRL 20 hours test according to the CEC-L-45-A-99 standard the viscosity of the lubricating composition is greater than 10.0 cSt and strictly less than 11.0 cSt, preferably less than or equal to 10.9 cSt for an oil initially of grade 50, and 20 (c) at 40*C after the KRL 3 hours test, according to the CEC-L-45-A-99 standard, the test duration of which is reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 50. Under these conditions, these compositions are particularly suitable for hot climates. 25 These conditions are determined by measurements of kinematic viscosity expressed in centistokes cSt (or equivalent mm 2 /s) and according to known methods for which the standards were referred to earlier in the text. (C) The base oils: The base oils used in the formulation of lubricants according to the present 30 invention are oils of groups I to II according to the API classification, of mineral, synthetic or natural origin, used alone or in mixture, one of the characteristics of which is insensitivity to shear, i.e. their viscosity does not change under shear. In the composition they represent at least 50 wt.%, relative to the total weight of the final 2424890_1 (GHMatters) 11 composition. Moreover, their content can represent up to 95% or even 98% in the final composition. Moreover, the lubricants according to the present invention necessarily comprise at least one base oil selected from the oils of groups I to II. Preferably, the lubricants 5 according to the present invention comprise at least 50 wt.%, preferably at least 70 wt.%, of one or more base oils selected from the oils of groups I to II. (D) The package of additives: The packages of additives used in the lubricating formulations according to the invention are conventional and are known by the skilled person and meet performance 10 levels defined by, among others, the ACEA (Association des constructeurs Europ6ens d'Automobiles - "European Automobile Manufacturers' Association") and/or the API (American Petroleum Institute). They contain in particular and non-limitatively: - antioxidants preventing degradation of the oil (for example amine or phenolic 15 derivatives) e antiwear and extreme-pressure agents protecting the rubbing surfaces by chemical reaction with the metallic surface (for example zinc dithiophosphate), - dispersants ensuring that insoluble solid contaminants (for example PIB succinimide) are kept in suspension and are removed, 20 - detergents, whether superbasic or not, preventing the formation of deposits on the surface of metal parts by dissolution of oxidation and combustion by-products (for example salicylates, phenates or sulphonates). and at least 30 wt.% of a diluent consisting of base oil and optionally viscosity improving polymer. 25 The percentage by weight of the package of additives based on the weight of the final composition according to the invention is at least 5%, the diluent being included in this percentage. (E) Compounds known as "pour point improvers" The lubricating formulations according to the invention optionally comprise a 30 pour point improver, which can be selected from the polymethacrylate (PMA) group with molecular weights generally between 5000 and 10000 daltons. It should be noted that these PMAs, when they are used as pour point improving additives, are typically present in the lubricating composition at a content of the order of 0.2 wt.%, based on 2424890.1 (GHMatters) 12 the weight of the final lubricating composition. These pour point improving additives are generally supplied in the form of formulations diluted to a varying extent in a base oil. In particular, when these formulations are not very dilute, the PMAs are present at a content of the order of 60%. 5 Their use in the polymer mixture according to the present invention for adjusting the viscosity of the lubricant to a certain level after shear may require the use of higher contents. (F) The polymer mixture in the lubricating composition. The viscosity profile previously mentioned is in particular obtained by means of a 10 mixture of at least two polymers selected from the polymers of types "A", "B" or "C" as defined below: The polymers of types "A", "B" or "C" used as a mixture in the lubricants according to the present invention are preferably selected from polymers that improve the viscosity index or improve the pour point, as described above. 15 The viscosity improving polymers used in the present invention correspond to those used in the monofunctional oils. They are preferably selected from poly-alpha olefins (PAO) with a kinematic viscosity at 100*C greater than 90 cSt, poly isobutenes (PIB), polymeric esters, olefinic copolymers (OCP), homopolymers or copolymers of styrene, of butadiene or of isoprene, polymethacrylates (PMA). 20 The pour point improving polymers used in the present invention are preferably selected from polymethacrylates (PMA). In general, the purpose of a viscosity improving polymer is to reduce the viscosity variations of the lubricant with the temperature. This temperature behaviour is characterized by the viscosity index V.I. of the lubricant. For an oil of high V.I. the 25 stability of its viscosity as a function of temperature will be better. The polymers incorporated in the lubricants according to the present invention have been classified in three groups according to the particular range of PSSI to which they belong: 1) The group of polymers of type "A" comprises the polymers that have a 30 permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100*C, less than or equal to 40. These polymers have little sensitivity to shear: they are polymers whose PSSI after the standardized KRL 20 hours test at 100*C is less than or equal to 40, preferably from 0 to 20. This type of polymer will make it 2424890_1 (GHMatters) 13 possible to maintain the viscosity at a sufficient level in the engine and in the gearbox, but will also allow the viscosity to drop considerably in the hydraulic system. The group of polymers of type "A" will include, in particular and non-limitatively, viscosity improving polymers selected from viscous poly-alpha-olefins (PAO) (with a 5 viscosity at 100*C greater than 90 cSt), polyisobutenes (PIB), polymethacrylates (PMA). More specifically the polymers of type A are viscosity improving polymers selected from the polymethacrylates (Viscoplex 0-030, 0-110, 6-054, 8-220, 12-310), viscous poly-alpha-olefins (Spectrasyn 1000,300,150), polyisobutenes (Indopole 2100, Lubrizol 3174), polymeric esters (Kenjetlube 2700). 10 2) The group of polymers of type "B" comprises polymers that have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 1 00*C, between 40 and 65 exclusive. These polymers of intermediate behaviour are said to be sensitive to shear: they are polymers whose PSSI after the standardized KRL 20 hours test at 100*C is between 40 and 65 exclusive. This type of 15 polymer will provide the extra viscosity improver if necessary. The group of polymers of type "B" includes in particular the viscosity improving polymers of the polymethacrylate type (Viscoplex 0-220, 3-500, 8-400, 8-251, 8-310). 3) The group of polymers of type "C" comprises polymers that have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours 20 test at 1 00*C, greater than or equal to 65. These polymers are very sensitive to shear: they are polymers whose PSSI after the standardized KRL 20 hours test at 100*C is greater than or equal to 65, preferably from 65 to 100. This type of polymer will be sheared very rapidly in the hydraulic system, with a subsequent, long-lasting drop in viscosity of the lubricant in said system, thus avoiding the problems of low 25 temperature starting. The group of polymers of type "C" includes, in particular and non-limitatively, the viscosity improving polymers selected from the category of olefinic copolymers, homopolymers or copolymers of styrene, of butadiene, or of isoprene. More specifically the polymers of type C are viscosity improving polymers selected from 30 polymethacrylates (Viscoplex 7-710), olefinic copolymers (Paratone 8006, Lubrizol 7077), hydrogenated styrene-isoprene copolymers (Shellvis 151, 201, 261 and 301), copolymeric esters (Lubrizol 3702). 2424890_1 (GHMaUers) 14 Thus, the viscosity profile of the composition according to the invention is obtained when at least two polymers of the mixture are selected from different ranges of PSSI. The polymer mixtures used in the invention are constituted by at least two 5 polymers, the polymers in the mixture differing from one another in that they belong to a different range of permanent shear stability index (PSSI) measured after the standardized KRL 20 hours test at 100*C. This difference is characterized by the existence of a difference in PSSI of at least 25 between the PSSIs of at least two of the polymers present in the mixture. 10 Moreover, the resistance to shear of a polymer is not connected exclusively with its chemical nature. It can also be connected with physicochemical parameters. In fact parameters such as the molecular weights, molecular weight distribution (characterized in particular by the polydispersity index of the polymer), the degree of branching of the polymer chains, and generally the morphological characteristics of 15 the polymer have an influence on its resistance to shear. Thus, certain compounds of identical chemical nature, such as the polymethacrylates for example, may belong to any one of the types "A", "B", or "C" described here. Accordingly, a person skilled in the art will select the polymers of different types for use in the mixture in relation to their classification according to type A, B or C and 20 their capacity for producing a lubricating composition, while meeting the three cumulative conditions as described above in the target viscosity profile. This viscosity profile is also obtained when the polymers of the mixture differ either in their chemical nature or in their physicochemical nature. Thus, when the polymers of the mixture differ in their chemical nature, this 25 differentiation originates from the preparation of the polymers from monomer units of a different chemical nature. Thus, for example, a polymethacrylate is chemically different from a polyisobutene. When the polymers of the mixture differ in their physicochemical nature, this differentiation arises from the preparation of the polymers from monomer units of 30 identical chemical nature. In this case, each polymer of the mixture differs in that it belongs to a different range of permanent shear stability index (PSSI) as well as by at least one physicochemical characteristic selected from the (number-average or weight-average) molecular weight or the molecular weight distribution of said 242480_1 (GHMater) 15 polymer characterized by its polydispersity index or the morphology of the three dimensional network of said polymer characterized by its degree of crosslinking and/or branching. These differences in physicochemical nature are utilized according to techniques that are well known in the field of polymers. 5 According to a particular embodiment, the compositions according to the invention comprise a mixture in all proportions of two polymers of type A/B or A/C or B/C. Preferably, in said mixture, the amount by weight of one of the polymers of type A or B or C relative to the total weight of polymer in the mixture ranges from 10 to 90%. According to a preferred embodiment the compositions comprise a mixture of 10 two polymers of type A and C in which the weight ratio A/C ranges from 10/90 to 90/10. According to another particular embodiment the compositions according to the invention comprise a mixture in all proportions of the three polymers A, B and C. In this mixture, the amount by weight of one of the polymers of type A or B or C relative 15 to the total weight of the polymers in the mixture can be at least 10% and at most 80%. Thus, preferably we can have mixtures A/B/C whose proportions by weight are 10/10/80 or 10/80/10 or 80/10/10 and all intermediate proportions. According to an embodiment, the compositions according to the invention comprise a mixture of the three polymers A, B and C in which polymer A is present in 20 an amount from 30 to 45 wt.%, polymer B is present in an amount from 1 to 20 wt.% and polymer C is present in an amount from 30 to 45 wt.%, these percentages being expressed relative to the total weight of the polymers. More particularly, the mixtures of polymers used in the invention as defined above represent at least 5%, preferably from 5 to 40%, more preferably 5 to 15 wt.%, based 25 on the weight of the final lubricating composition. According to an embodiment the minimum amount of a polymer relative to the total weight of the final composition is 1%. In the field of lubricants all these percentages generally correspond to polymers that comprise at least 5% of polymeric active substance, the remainder being 30 represented by a base oil used as a diluent. Moreover, in certain cases when the polymer requires little or no dilution (for example the PAOs), these percentages can be up to 100% of polymeric active substance. 2424890_1 (GHMatters) 16 Consequently, these lubricants adapt very rapidly to the conditions of use required in each mechanism. In order to prepare the lubricating composition according to the invention, a mixture of at least two polymers of type A, B or C is incorporated, generally at a 5 temperature between 20 and 100'C and at atmospheric pressure, in at least one oil of groups I to II optionally comprising a package of additives and optionally a pour point improver. The polymers of type "A", "B" or "C" according to the present invention can be incorporated in the composition in the form of separate components, or else they can 10 be introduced as a component of the package of additives, as an additive or a diluent. Thus, the lubricating compositions according to the invention are prepared by incorporating at least one of the viscosity improving polymers of type A, B, or C directly in the composition as a separate additive, independently of the package of additives. 15 According to another embodiment, all or part of at least one of the viscosity improving polymers of type A, B, or C is incorporated in the lubricant as an element of a package of additives. According to another embodiment all or part of at least one of the viscosity improving polymers of type A, B, or C is incorporated in the lubricant as a diluent in 20 the package of additives. The compositions according to the invention are used as a single lubricant in various mechanisms of motor vehicles simultaneously, in particular in mechanisms having different shear rates. Thus, the compositions according to the invention have a performance that is particularly well suited for good high-temperature stability in the 25 engine and the transmission and for cold starting of the hydraulic system. 242480_1 (GHMatters) 17 Examples: The examples given below are for the purpose of illustrating the invention without limiting its scope. The mixtures were prepared with stirring at 80'C in 1-litre bottles. The ASTM D445 standard is applied for the determination of kinematic viscosities. Two samples 5 of lubricants were prepared, of grade 40 and 50 respectively according to the SAE J 300 classification. Example 1: A lubricant was prepared containing 69.1 wt.% of a base oil of group I having a viscosity of 3.53 cSt at 100 0 C, and 15.4 wt.% of a commercial package of additives. 10 This package of additives did not contain any polymers of type "A", "B" or "C" according to the present invention, and the diluent was constituted by base oil. A mixture consisting of: 13 wt.% of a poly-alpha-olefin of type "A" according to the present invention, having a PSSI of 35, and 15 2.5 wt.% of a formulation containing approximately 9% of active substance represented by a hydrogenated styrene-isoprene copolymer of type "C" according to the present invention, having a PSSI of 90 was then added to said lubricant. The lubricant thus prepared is of grade 40 according to the SAE J300 20 classification. Its kinematic viscosity at 100 0 C before shear is 15.66 cSt. Example 2: A lubricant was prepared containing 68.35 wt.% of a base oil of group I with a viscosity of 3.53 cSt at 100 0 C, and 15.4 wt.% of a commercial package of additives. 25 This package of additives did not contain any polymers of type "A", "B" or "C" according to the present invention and the diluent was constituted by base oil. A mixture consisting of: 13.25 wt.% of a poly-alpha-olefin of type "A" according to the present invention, having a PSSI of 35, and 30 3.0 wt.% of a formulation containing approximately 9% of active substance represented by a hydrogenated styrene-isoprene copolymer of type "C" according to the present invention, having a PSSI of 90 was then added to said lubricant. 5360116 1 (GHMatters) P85298.AU 18 The lubricant thus prepared was of grade 50 according to the SAE J300 classification. Its kinematic viscosity at 100 C before shear is 16.59 cSt. Table 1 below gives the viscosity values in cSt of these lubricating compositions: 5 initial, at 1 00*C, before shear at 1 00*C after the KRL-20 hours test according to the CEC-L-45-A-99 standard, at 1 00*C after the Bosch-30 cycles test according to the CEC-L- 1 4-A-93 standard, at 40'C after the KRL-3 hours test, according to the CEC-L-45-A-99 standard with the test duration reduced to 3 hours. 10 Table I: Example I Example 2 Base oils % by mass % by mass Group I with a viscosity of 3.53 cSt 69.1 68.35 (% of total weight of lubricant) Packages of additives 15.4 15.4 VI improving polymers/ PSSI Type "A" Spectrasyn 1000/ PSSI 35 13.0 13.25 Type "C" ShellVis 301/ PSSI 90 2.5 3 Single lubricating composition Grade 40 Grade 50 Viscosity at 100 0 C before shear, in cSt 15.66 16.59 Viscosity at 40*C after KRL 3H (hydraulics) in cSt 70.0 71.60 Viscosity at 100*C after KRL 20H (gearbox) in cSt 10.82 10.98 Viscosity at 100*C after Bosch 30 cycles (engine) in cSt 14.0 15.03 Spectrasyn 1000 is a poly-alpha-olefin (PAO) SV 301 is a hydrogenated styrene-butadiene copolymer 15 The package of additives is a package of commercial additives for engine oil diluted in oils of group I not containing any polymer of types A, B or C according to the present invention. This package makes it possible in particular to formulate lubricants for engines 20 having performances at level E3 or higher of the ACEA. 242480_1 (GHMetSts) 18a In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to 5 preclude the presence or addition of further features in various embodiments of the invention. 5360116 1 (GHMatters) P85298.AU

Claims

1. A lubricating composition comprising at least one base oil of groups I to II and a mixture of at least two polymers having a difference of permanent shear stability 5 index (PSSI), measured after the standardized KRL 20 hours test at 100 0 C of at least 25, and having a viscosity profile such that: (a') at 100 0 C, before shear, the kinematic viscosity of the new lubricating composition is greater than 15.0 cSt and less than 16.3 cSt, (a) at 100 0 C after the Bosch-30 cycles test according to standard CEC-L-14-A-93 10 the kinematic viscosity of the final lubricating composition is greater than 12.0 cSt for an oil initially of grade 40, (b) at 100 0 C after the KRL-20 hours test according to standard CEC-L-45-A-99 the viscosity of the lubricating composition is greater than 10.0 cSt for an oil initially of grade 40, and 15 (c) at 40'C after the KRL-3 hours test, according to standard CEC-L-45-A-99 with the test duration reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 40.

2. A lubricating composition comprising at least one base oil of groups I to II, 20 and a mixture of at least two polymers having a difference of permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100 0 C of at least 25, and having a viscosity profile such that: (a') at 100 0 C, before shear, the kinematic viscosity of the fresh lubricating composition is greater than 16.3 cSt and less than 21.9 cSt, 25 (a) at 100 0 C after the Bosch-30 cycles test according to standard CEC-L-14-A-93 the kinematic viscosity of the final lubricating composition is greater than 15.0 cSt for an oil initially of grade 50, (b) at 100 C after the KRL-20 hours test according to standard CEC-L-45-A-99 the viscosity of the lubricating composition is greater than 10.0 cSt and strictly less than 30 11.0 cSt for an oil initially of grade 50, and (c) at 40'C after the KRL-3 hours test, according to standard CEC-L-45-A-99 with the test duration reduced to 3 hours, the viscosity of the lubricating composition is between 61 and 75 cSt for an oil initially of grade 50. 5360116 1 (GHMatters) P85298.AU 20

3. The lubricating composition according to any one of claims 1 to 2 comprising at least 50 wt.%, based on the weight of the final composition, of one or more base oils including at least one oil selected from the oils of groups I to II and at least 5% wt.% based on the weight of the final composition, of a mixture comprising at least two 5 different polymers of type "A", "B", or "C", each of the polymers of the mixture differing from one another in that they belong to a separate range of permanent shear stability index (PSSI) such that: -the polymers of type "A" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100 0 C, less than or equal to 40, 10 -the polymers of type "B" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100 0 C, between 40 and 65 exclusive; -the polymers of type "C" have a permanent shear stability index (PSSI), measured after the standardized KRL 20 hours test at 100 C, greater than or equal to 65; composition in which at least two polymers have a difference in PSSI measured 15 after the standardized KRL 20 hours test at 100 0 C, of at least 25.

4. The lubricating composition according to any one of claims 1 to 3, comprising at least 50 wt.% of one or more base oils selected from the oils of groups I to II. 20

5. The lubricating composition according to any one of claims 3 to 4, wherein each of the polymers of the mixture is obtained from monomer units of a different chemical nature. 25

6. The lubricating composition according to any one of claims 3 to 5, wherein each polymer of the mixture is obtained from monomer units of identical chemical nature, and the polymers of the mixture differ from one another in that they belong to a different range of permanent shear stability index (PSSI) measured after the standardized KRL 20 hours test at 100 0 C and by at least one physicochemical 30 characteristic selected from the number-average or weight-average molecular weight, the molecular weight distribution of said polymer characterized by the polydispersity index, the morphology of the three-dimensional network of said polymer characterized by its degree of crosslinking and/or branching. 5360116 1 (GHMatters) P85298.AU 21

7. The lubricating composition according to any one of claims 3 to 6, wherein, in the mixture comprising at least two polymers, the amount of one polymer relative to the total weight of the polymer mixture ranges from 10% to 90%. 5

8. The lubricating composition according to any one of claims 3 to 7, wherein the mixture comprises two polymers, one of type A and the other of type C.

9. The lubricating composition according to claim 8, wherein the weight ratio of the mixture of the two polymers A/C ranges from 10/90 to 90/10. 10

10. The lubricating composition according to any one of claims 3 to 9, additionally comprising from 5 to 30 wt.%, relative to the weight of the final composition, of a package of functional additives and optionally less than 1 wt.% relative to the weight of the final composition, of a pour point improver. 15

11. The lubricating composition according to any one of claims 3 to 10, wherein the polymers of the mixture are selected from polymers of the viscosity improver type and optionally from polymers of the pour point improver type. 20

12. The lubricating composition according to claim 11, wherein the viscosity improving polymers are selected from poly-alpha-olefins (PAO) with a kinematic viscosity at 100 0 C greater than 90 cSt, poly-isobutenes (PIB), polymeric esters, olefinic copolymers (OCP), homopolymers or copolymers of styrene, of butadiene or of isoprene, polymethacrylates (PMA). 25

13. The lubricating composition according to claim 11, wherein the pour point improving polymers are selected from polymethacrylates (PMA).

14. The lubricating composition according to any one of claims 3 to 13, 30 wherein the polymers of type A are viscosity improving polymers selected from polymethacrylates, poly-alpha-olefins with a kinematic viscosity at 100 0 C greater than 90 cSt, polyisobutenes, polymeric esters. 5360116 1 (GHMatters) P85298.AU 22

15. The lubricating composition according to any one of claims 3 to 13, wherein the polymers of type C are viscosity improving polymers selected from polymethacrylates, olefinic copolymers, hydrogenated styrene-isoprene copolymers, copolymeric esters. 5

16. The lubricating composition according to any one of claims 3 to 13, wherein the polymers of type B are viscosity improving polymers of the polymethacrylate type. 10

17. The lubricating composition according to any one of claims 3 to 16 having the characteristics defined in claim 1 or 2.

18. A method of making the lubricating composition according to one of claims 1 to 17, wherein a mixture comprising at least two different polymers is 15 incorporated in at least one oil of groups I to II optionally comprising a package of additives and optionally a pour point improver.

19. The method according to claim 18 of making the lubricating composition according to any one of claims 1 to 17, wherein at least one of the polymers of the 20 mixture is a viscosity improver which is incorporated directly in the composition as a separate compound, independently of the package of additives.

20. The method according to claim 18 of making the lubricating composition according to any one of claims 1 to 17, wherein all or part of at least one of the 25 viscosity improving polymers of the mixture is incorporated in the composition as an element of the package of additives.

21. The method according to claim 18 of making the lubricating composition according to one of claims 1 to 17, wherein all or part of at least one of the viscosity 30 improving polymers of the mixture is incorporated in the composition in the form of a diluent of the package of additives.

22. The use of the lubricating composition according to any one of claims 1 to 17 as a single fluid for lubricating various mechanisms of motor vehicles. 5360116 1 (GHMatters) P85298.AU 23

23. The use according to claim 22, wherein the single fluid is used for lubricating at least three mechanisms of motor vehicles: the engine, the gearbox and the hydraulic system of the vehicle. 5

24. The use according to claim 22 or 23, wherein the single fluid is also used for lubricating the circuit for operating the brakes, the on-board compressor and optionally other ancillary mechanisms.

25. A lubricating composition as defined in claim 1 or 2, or a method of 10 making the lubricating composition, or a use of the lubricating composition, substantially as herein described with reference to the Examples. 5360116 1 (GHMatters) P85298.AU