LUBRICANT COMPOSITIONS FOR HIGH EFFICIENCY ENGINES

Abstract

The instant disclosure is directed to a method of lubricating a sump-lubricated, high efficiency, gasoline-fueled internal combustion engine. Said method involves supplying to the engine a lubricating composition comprising an oil of lubricating viscosity, an anti-wear agent, an ashless antioxidant, a metal-containing detergent, an ashless polyolefin dispersant, and (f) a polymeric viscosity modifier. The disclosure further provides a method of operating a high efficiency sump-lubricated gasoline-fueled internal combustion engine while maintaining or improving at least one of durability, deposit control, oxidation control, fuel economy, and resistance to knock and stochastic pre-ignition.

Claims

1. A method of lubricating an internal combustion engine, comprising supplying to a sump-lubricated, high efficiency, gasoline-fueled internal combustion engine a lubricating composition comprising (a) an oil of lubricating viscosity, (b) an anti-wear agent in an amount 0.15 weight percent to 6 weight percent of the composition, (c) an ashless antioxidant in an amount 1.2 weight to 7 weight percent of the composition, and (d) a metal-containing detergent in an amount to deliver 0.2 weight percent sulfated ash up to 1.5 weight percent sulfated ash to the composition, (e) an ashless polyolefin dispersant in an amount 0.8 weight percent to 8 weight percent of the composition, and (f) a polymeric viscosity modifier, dispersant viscosity modifier, or mixtures thereof in an amount 0.1 weight percent to 4.5 weight percent of the composition.

2. The method of claim 1, wherein the internal combustion engine is operated at an effective compression ratio of at least 15:1.

3. The method of claim 1, wherein the internal combustion engine is operated under a load with a brake mean effective pressure (BMEP) of greater than or equal to 18 bars.

4. The method of claim 1, wherein the gasoline has an octane rating of at least 95 by the (R+M)/2 method.

5. The method of claim 1, wherein the internal combustion engine is spark ignited.

6. The method of claim 1, wherein the internal combustion engine is compression ignited.

7. The method of claim[[s]] 1 to 6, wherein the internal combustion engine is a gasoline direct injection (GDI) engine.

8. The method of claim 1, wherein the internal combustion engine is equipped with a turbocharger, a super charger, an air booster, or combinations thereof.

9. The method of claim 1, wherein the internal combustion engine is operated with variable valve timing.

10. The method of claim 1, wherein the internal combustion engine is operated with an air-fuel equivalence ratio (X) of less than 1.2.

11. The method of claim 1, wherein the internal combustion engine is operated at speeds less than or equal to 3000 rpm.

12. The method of any of claim 1, wherein the anti-wear additive comprises a phosphorus-containing additive, a phosphorus-free additive, or combinations thereof.

13. The method of claim 12, wherein the phosphorus-containing additive is selected from metal dialkyldithiophosphates, amino phosphate salts, hydrocarbyl phosphites, hydrocarbyl phosphines, hydrocarbyl phosphonates, and combinations thereof.

14. The method of claim 12, wherein the phosphorus-free anti-wear additive is selected from hydrocarbyl esters, amides, or imides of hydroxy-substituted carboxylic acid acids and mixtures thereof.

15. The method of claim 1, wherein the metal detergent is a selected from a neutral alkaline earth metal detergent, an overbased alkaline earth metal detergent, and combinations thereof.

16. The method of claim 15, wherein the alkaline earth metal detergent comprises calcium detergents, magnesium detergent, and mixtures thereof.

17. The method of claim 1, wherein the oil of lubricating viscosity has a kinematic viscosity of at least 4.2 m.sup.2/s at 100 C.

18. The method of claim 1, wherein the lubricant composition has a viscosity grade according to SAE J300 of XW-YY, wherein X is 0, 5, 10 or 15, and YY is 8, 12, 16, 20, 30, or 40.

19. A method of operating an internal combustion engine, comprising supplying to a sump-lubricated, high efficiency, gasoline-fueled internal combustion engine a lubricating composition comprising (a) an oil of lubricating viscosity, (b) an anti-wear agent in an amount 0.15 weight percent to 6 weight percent of the composition, (c) an ashless antioxidant in an amount 1.2 weight to 7 weight percent of the composition, and (d) a metal-containing detergent in an amount to deliver 0.2 weight percent sulfated ash up to 1.5 weight percent sulfated ash to the composition, (e) an ashless polyolefin dispersant in an amount 0.8 weight percent to 8 weight percent of the composition, and (f) a polymeric viscosity modifier, dispersant viscosity modifier, or mixtures thereof in an amount 0.1 weight percent to 4.5 weight percent of the composition.

20. A method of reducing friction power loss in a sump-lubricated, high efficiency, gasoline-fueled internal combustion engine comprising operating said engine and lubricating said engine with a lubricant composition comprising (a) an oil of lubricating viscosity, (b) an anti-wear agent in an amount 0.15 weight percent to 6 weight percent of the composition, (c) an ashless antioxidant in an amount 1.2 weight to 7 weight percent of the composition, and (d) a metal-containing detergent in an amount to deliver 0.2 weight percent sulfated ash up to 1.5 weight percent sulfated ash to the composition, (e) an ashless polyolefin dispersant in an amount 0.8 weight percent to 8 weight percent of the composition, and (f) a polymeric viscosity modifier, dispersant viscosity modifier, or mixtures thereof in an amount 0.1 weight percent to 4.5 weight percent of the composition.

Description

EXAMPLES

[0166] Embodiments will be further illustrated by the following examples, which set forth particularly advantageous embodiments. While the examples are provided to illustrate certain embodiments, they are not intended to limiting.

Lubricating Compositions

[0167] A series of OW-20 engine lubricants in Group III base oil of lubricating viscosity are prepared containing the anti-wear additives described above as well as conventional additives including polymeric viscosity modifier, ashless succinimide dispersant, overbased detergents, antioxidants (combination of phenolic ester and diarylamine), as well as other performance additives as follows (Table 1). The phosphorus, sulfur and ash contents of each of the examples are also presented in the table in part to show that each example has a similar amount of these materials and so provide a proper comparison between the comparative and examples according to embodiments described herein.

TABLE-US-00004 TABLE 1 Lubricating Oil Composition Formulations.sup.1 EX1 EX2 EX3 EX4 C3/6 Secondary ZDDP 0.79 0.79 0.79 0.79 Ashless Antiwear.sup.2 0 0.48 0 0.48 Overbased Calcium Sulfonate.sup.3 0.74 0.74 0.58 0.58 PIBsuccinimide dispersant.sup.4 2 2 2 2 Na Sulfonate 0.16 0.16 0 0 Overbased Mg Sulfonate 0 0 0.58 0.58 Ashless Antioxidant.sup.5 1.5 1.5 1.45 1.45 PMA VI Improver.sup.6 2.1 2.1 0 0 E-P VI Improver.sup.7 0 0 0.5 0.5 Additional Additives.sup.8 0.28 0.28 0.25 0.25 .sup.1All amounts shown above are in weight percent and are on an oil-free basis unless otherwise noted. .sup.2Oleyl tartrimide .sup.3Combination of 500 and 700 TBN (oil free) overbased calcium sulfonates .sup.4PIBsuccinimide prepared from 2000 Mn PIB with oil free TBN of 27 mg KOH/g .sup.5Combination of alkylated diarylamine, hindered phenol, and sulfurized olefin antioxidants .sup.6High VI Mw polymethacrylate .sup.7Ethylene-propylene copolymer .sup.8The Additional Additives used in the examples include friction modifier, pourpoint depressants, anti-foam agents, emulsifier, titanium alkoxide, and includes some amount of diluent oil

[0168] Testing

[0169] Using advanced power-cylinder simulation tools, current engine technologies can be simulated and extrapolated forward into the realm of future combustion conditions. This simulation allows for the measurement of the impact of lubricant compositions to reduce transmitted force and therefore tribocouple stress over a wide range of operating conditions. Under conditions designed to simulate modern and future high compression engines it was found that LZ surface active additive systems can have a large impact in reducing tribocouple stress and decreasing friction power loss, particularly during the power-stroke. Ring on Bore Testing

[0170] Increasing compression ratio means combustion pressures will essentially rise. Increased combustion pressures result in higher piston ring loading on the cylinder bore wall and so the two are physically linked. Using knowledge of contact dynamics and geometry it is possible to perform calculations to relate combustion pressures to dynamic load in the ring-on-bore apparatus.

[0171] The ring on bore apparatus consists of a section of piston ring cut from actual engine hardware which is reciprocated against a section of cylinder bore material removed from the same engine, and in the presence of the lubricant under investigation. This approach allows in-cylinder dynamics to be closely replicated. The test is carried out at 1000 rpm and 100 C.; and is designed to simulate typical engine conditions. Dynamic loading is increased incrementally to simulate engines with increased combustion pressure. Steady-state load (applied during the three pumping strokes) is set at 25N for every experiment as this simulates ring tension only and is typical of in-cylinder dynamics.

[0172] The experiment starts at low loads which simulate low power gasoline engines. The dynamic load is ramped up incrementally while holding all other experimental conditions constant. Dynamic load (simulating combustion pressure) is increased from low to high, to simulate current engines, high efficiency engines, and above where current engines can operate. This procedure is repeated identically using lubricants of differing composition to allow for scientific comparison to be made.

TABLE-US-00005 TABLE 2 Power Loss Testing: Peak Transmitted Force Peak Combustion Load (N) 75 100 125 150 175 200 225 250 275 EX1 (N) 8.63 11.7 14.6 18 20.9 24.2 27.4 30.8 33.9 EX2 (N) 7.16 9.15 12 14.4 16.6 20.2 22.9 25.2 28.2

[0173] The data indicates that in this simulation of a high compression engine (as indicated by the increase in peak combustion load), the lubricating composition with the boosted anti-wear system reduced force transmission from the piston ring to the power cylinder surface. This reduced force reduces stress in the tribocouple, and so limits the propensity for contact derived wear to occur.

[0174] Additional testing was carried out to evaluate the impact of viscosity on efficiency in simulated high compression regimes. Experiments were conducted to evaluate the ability of viscous fluids in reducing peak powerstroke friction power loss. Performance gains can be realized by interposing a viscous film in the power-cylinder tribocouple during the power-stroke.

[0175] The Approximate SAE grade viscosity fluids tested show the propensity of the fluid element to offset the transition from fluid lubrication regimes to the regimes of contact. This results in a net reduction of transmitted force during the power-stroke. These experiments were carried using synthetic Group V polyalphaolefin base oil with a kinematic viscosity of 8 cSt. The base oil is heated while transmitted force under dynamic conditions is measured. This creates a sweep of all SAE grade viscosities and their performance (Table 3).

TABLE-US-00006 TABLE 3 Viscosity Impact on Power Losses Viscosity Simulated SAE Temperature PowerStroke Mean (mPas) Grade (C.) Dynamic FF (N) 82.36 20 1.37 51.02 30 1.47 32.42 40 1.73 21.99 60 50 2.23 15.6 50 60 2.64 11.77 40 70 3.16 9.22 30 80 3.17 7.32 20 90 3.36 6.09 16 100 3.42 5.42 12 110 3.66 4.47 120 3.69 3.93 8 130 3.79 3.43 140 4

[0176] Table 3 demonstrates that increasing viscosity between the ranges of SAE 8 to SAE 60.sup.+ provides reduced transmitted force for the tribocouple under dynamic conditions specifically designed to mechanically simulate combustion event tribology for high efficiency engines. This result shows that increased viscosity during the combustion event reduces friction powerloss of the high efficiency engine, further contributing to the engines efficiency. The result also suggests that the durability of the power-cylinder tribocouple is improved, primarily due to the reduced surface stress imparted by the surface-separating fluid lubricant layer which exists for longer duration during the combustion event.

[0177] It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. The products formed thereby, including the products formed upon employing lubricant composition in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the disclosed embodiments; the lubricating compositions disclosed herein encompass lubricant compositions prepared by admixing the components described above.

[0178] Each of the documents referred to above is incorporated herein by reference, as is the priority document and all related applications, if any, which this application claims the benefit of Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word about. Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the disclosed lubricating compositions may be used together with ranges or amounts for any of the other elements.

[0179] As used herein, the term hydrocarbyl substituent or hydrocarbyl group is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring); (ii) substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this disclosure, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulphoxy); (iii) hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this disclosure, contain other than carbon in a ring or chain otherwise composed of carbon atoms.

[0180] Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

[0181] While the instant disclosure has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the instant disclosure is intended to cover such modifications as fall within the scope of the appended claims.