Lubricating oil compositions

1. A method of reducing wear in an internal combustion engine, comprising:

using as the crankcase lubricating oil for said engine a lubricant composition comprising:

a major amount of base oil;

a first dispersant and a second dispersant each independently comprising at least one member selected from the group consisting of hydrocarbyl-substituted succinimides, hydrocarbyl-substituted amines, and Mannich base adducts derived from hydrocarbyl-substituted phenols condensed with aldehydes and amines;

wherein the hydrocarbyl substituent of the first dispersant has a number average molecular weight ranging from about 1500 to about 2500 as determined by gel permeation chromatography,

wherein the hydrocarbyl substituent of the second dispersant has a number average molecular weight ranging from about 800 to about 1200 as determined by gel permeation chromatography, and

wherein the hydrocarbyl-substituent of at least one of the first and second dispersants comprises a polymerization product derived from a reaction mixture comprising (i) from about 55 to about 65 weight percent raffinate I stream and (ii) from about 35 to about 45 weight percent isobutylene, with the proviso that (i) and (ii) are different; and

a minor viscosity index improving amount of a non-shear stable viscosity index improver comprising a substantially linear block copolymer having a number average molecular weight as determined by gel permeation chromatography ranging from about 50,000 to about 250,000, the block copolymer being derived from a conjugated diene monomer containing no less than 5 carbon atoms and a styrene monomer, wherein the block copolymer has a styrene content ranging from about 30 wt. % to about 40 wt. %, and an olefinic unsaturation ranging from about 0.5 wt. % to about 5 wt. %.

2. The method of claim 1 , wherein the conjugated diene monomer comprises isoprene.

3. The method of claim 1 , wherein the internal combustion engine is a gasoline or diesel internal combustion engine.

4. The method of claim 1 , wherein at least one of the first and second dispersants comprises a hydrocarbyl-substituted succinic acid derivative.

5. The method of claim 1 , wherein the first dispersant is a post treated dispersant.

6. The method of claim 1 , wherein at least one of the first and second dispersants comprises a Mannich base adduct derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine.

7. A method for lubricating a crankcase in an internal combustion engine comprising:

using in said crankcase a lubricant composition comprising a mineral oil base stock and a lubricant additive in an amount sufficient to enhance the dispersability of particles in the lubricant composition, the lubricant additive comprising:

(a) a first dispersant and a second dispersant each independently comprising at least one member selected from the group consisting of hydrocarbyl-substituted succinimides, hydrocarbyl-substituted amines, and Mannich base adducts derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine;

wherein the hydrocarbyl substituent of the first dispersant has a number average molecular weight ranging from about 1500 to about 2500 as determined by gel permeation chromatography,

wherein the hydrocarbyl substituent of the second dispersant has a number average molecular weight ranging from about 800 to about 1200 as determined by gel permeation chromatography, and

wherein the hydrocarbyl-substituent of at least one of the first and second dispersants comprises the polymerization product of a reaction mixture comprising (i) from about 55 to about 65 weight percent raffinate I stream and (ii) from about 35 to about 45 weight percent isobutylene, with the proviso that (i) and (ii) are different; and

(b) a viscosity index improver comprising a substantially linear block copolymer having A number average molecular weight as determined by gel permeation chromatography ranging from about 50,000 to about 250,000, the block copolymer being derived from a conjugated diene monomer containing no less than 5 carbon atoms and a styrene monomer, wherein the block copolymer has a styrene content ranging from about 30 wt. % to about 40 wt. %, and an olefinic unsaturation ranging from about 0.5 wt. % to about 5 wt. %.

8. The method of claim 7 , wherein the conjugated diene monomer comprises isoprene.

9. The method of claim 7 , wherein at least one of the first and second dispersants comprises a hydrocarbyl-substituted succinic acid derivative.

10. The method of claim 7 , wherein the first dispersant is a post treated dispersant.

11. The method of claim 7 , wherein at least one of the first and second dispersants comprises a Mannich base adduct derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine.

12. A method of reducing wear in an internal combustion engine comprising:

using as the automatic transmission fluid for said engine a fluid composition comprising a mineral oil base stock and an additive in an amount sufficient to enhance the dispersability of particles in the lubricant composition, the additive comprising:

(a) a first dispersant and a second dispersant each independently comprising at least one member selected from the group consisting of hydrocarbyl-substituted succinimides, hydrocarbyl-substituted amines, and Mannich base adducts derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine;

wherein the hydrocarbyl substituent of the first dispersant has a number average molecular weight ranging from about 1500 to about 2500 as determined by gel permeation chromatography,

wherein the hydrocarbyl substituent of the second dispersant has a number average molecular weight ranging from about 800 to about 1200 as determined by gel permeation chromatography, and

wherein the hydrocarbyl-substituent of at least one of the first and second dispersants comprises the polymerization product of a reaction mixture comprising (i) from about 55 to about 65 weight percent raffinate I stream and (ii) from about 35 to about 45 weight percent isobutylene, with the proviso that (i) and (ii) are different; and

(b) a viscosity index improver comprising a substantially linear block copolymer having a number average molecular weight as determined by gel permeation chromatography ranging from about 50,000 to about 250,000, the block copolymer being derived from a conjugated diene monomer containing no less than 5 carbon atoms and a styrene monomer, wherein the block copolymer has a styrene content ranging from about 30 wt. % to about 40 wt. %, and an olefinic unsaturation ranging from about 0.5 wt. % to about 5 wt. %.

13. The method of claim 12 , wherein the conjugated diene monomer comprises isoprene.

14. The method of claim 12 , wherein at least one of the first and second dispersants comprises a hydrocarbyl-substituted succinic acid derivative.

15. The method of claim 12 , wherein the first dispersant is a post-treated dispersant.

16. The method of claim 12 , wherein the at least one of the first and second dispersants comprises a Mannich base adduct derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine.

17. The method of claim 12 , wherein the additive comprises the first dispersant in an amount ranging from about 45% to about 65% by weight, relative to the total weight of the additive composition.

18. The method of claim 12 , wherein the additive comprises the second dispersant in an amount ranging from about 35% to about 45% by weight, relative to the total weight of the additive composition.

19. The method of claim 12 , wherein the fluid composition comprises from about 1% to about 10% by weight of total dispersant, relative to the total weight of the fluid composition.

20. The method of claim 12 , wherein the fluid composition comprises from about 3% to about 6% by weight of total dispersant, relative to the total weight of the fluid composition.

21. A method for lubricating moving parts in a drive train of an internal combustion engine comprising:

using as the lubricating oil for said drive train a lubricant composition comprising a mineral oil base stock and a lubricant additive in an amount sufficient to enhance the dispersability of particles in the lubricant composition, the lubricant additive comprising:

(a) a first dispersant and a second dispersant each independently comprising at least one member selected from the group consisting of hydrocarbyl-substituted succinimides, hydrocarbyl-substituted amines, and Mannich base adducts derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine;

wherein the hydrocarbyl substituent of the first dispersant has a number average molecular weight ranging from about 1500 to about 2500 as determined by gel permeation chromatography,

wherein the hydrocarbyl substituent of the second dispersant has a number average molecular weight ranging from about 800 to about 1200 as determined by gel permeation chromatography, and

wherein the hydrocarbyl-substituent of at least one of the first and second dispersants comprises the polymerization product of a reaction mixture comprising (i) from about 55 to about 65 weight percent raffinate I stream and (ii) from about 35 to about 45 weight percent isobutylene, with the proviso that (i) and (ii) are different; and

(b) a viscosity index improver comprising a substantially linear block copolymer having a number average molecular weight as determined by gel permeation chromatography ranging from about 50,000 to about 250,000, the block copolymer being derived from a conjugated diene monomer containing no less than 5 carbon atoms and a styrene monomer, wherein the block copolymer has a styrene content ranging from about 30 wt. % to about 40 wt. %, and an olefinic unsaturation ranging from about 0.5 wt. % to about 5 wt. %.

22. The method of claim 21 , wherein the moving parts comprise a transaxle or gear.

23. The method of claim 22 , wherein the conjugated diene monomer comprises isoprene.

24. The method of claim 22 , wherein at least one of the first and second dispersants comprises a hydrocarbyl-substituted succinic acid derivative.

25. The method of claim 22 , wherein the first dispersant is a post-treated dispersant.

26. The method of claim 22 , wherein the at least one of the first and second dispersants comprises a Mannich base adduct derived from a hydrocarbyl-substituted phenol condensed with an aldehyde and an amine.

27. The method of claim 22 , wherein the lubricant additive comprises the first dispersant in an amount ranging from about 45% to about 65% by weight, relative to the total weight of the additive composition.

28. The method of claim 22 , wherein the lubricant additive comprises the second dispersant in an amount ranging from about 35% to about 45% by weight, relative to the total weight of the additive composition.

29. The method of claim 22 , wherein the lubricant composition comprises from about 1% to about 10% by weight of total dispersant, relative to the total weight of the lubricant composition.

30. The method of claim 22 , wherein the lubricant composition comprises from about 3% to about 6% by weight of total dispersant, relative to the total weight of the lubricant composition.

31. The method of claim 1 , wherein the lubricant composition comprises from about 1% to about 10% by weight of total dispersant, relative to the total weight of the lubricant composition.

32. The method of claim 1 , wherein the lubricant composition comprises from about 3% to about 6% by weight of total dispersant, relative to the total weight of the lubricant composition.

33. The method of claim 1 , wherein the lubricant additive comprises the first dispersant in an amount ranging from about 45% to about 65% by weight, relative to the total weight of the additive composition.

34. The method of claim 1 , wherein the lubricant additive comprises the second dispersant in an amount ranging from about 35% to about 45% by weight, relative to the total weight of the additive composition.

35. The method of claim 7 , wherein the lubricant composition comprises from about 1% to about 10% by weight of total dispersant, relative to the total weight of the lubricant composition.

36. The method of claim 7 , wherein the lubricant composition comprises from about 3% to about 6% by weight of total dispersant, relative to the total weight of the lubricant composition.

37. The method of claim 7 , wherein the lubricant additive comprises the first dispersant in an amount ranging from about 45% to about 65% by weight, relative to the total weight of the additive composition.

38. The method of claim 7 , wherein the lubricant additive comprises the second dispersant in an amount ranging from about 35% to about 45% by weight, relative to the total weight of the additive composition.