Lubricant additive compositions having improved viscosity index increase properties

摘要

A lubricant composition, additive concentrate, and method for lubricating an engine. The crankcase lubricant has less than 30 weight percent of a relatively low Noack volatility base oil and a viscosity additive. The viscosity additive has a minor effective amount of sacrificial polymeric viscosity index improver having a shear stability index (SSI) of greater than about 45 and a major amount of a viscosity index improver having an SSI of less than about 26. The minor amount of sacrificial viscosity index improver additive is effective to provide a lubricant composition having a ratio of absolute viscosity increase at 40° C. to an absolute viscosity increase at 40° C. of an RL 216 reference oil of less than about 0.8.

主权项

1. A lubricant composition comprising (i) a base oil that is devoid of 30 weight percent or more of a Group III base oil, a Group IV base oil, or a mixture thereof, wherein each of the Group III base oil and Group IV base oil have a Noack volatility of 15 wt. % or less and (ii) a viscosity additive comprising (a) from about 0.5 to about 3.0 wt. % of a polymeric viscosity index improver having a shear stability index (SSI) of greater than about 45 comprising a shear stable, dispersant polyalkyl(meth)acrylate viscosity index improver that is a polymeric reaction product of butylmethacrylate, lauryl methacrylate, cetyl methacrylate, and dimethylaminopropyl methacrylamide and (b) from about 5 to about 15 wt. % of a viscosity index improver having an SSI of less than about 26 based on a total weight of the lubricant composition, comprising an olefin copolymer viscosity index improver derived from ethylene and an olefin having from about 3 to about 23 carbon atoms, and wherein the viscosity index improver having an SSI of greater than about 45 is effective to provide a crankcase lubricant composition for an engine oil with an absolute viscosity increase at 40° C. of less than about 90 mm2/sec. and a ratio of absolute viscosity increase at 40° C. relative to an absolute viscosity increase at 40° C. of an RL 216 reference oil in a PEUGEOT TU5 engine test of less than about 0.8.