Lubricating Composition Containing Viscosity Modifier Combination

Abstract

The present invention relates to a lubricating composition containing (a) an oil of lubricating viscosity, (b) a star polymer and (c) a substantially linear polymer with a weight average molecular weight of 45,000 or less. The invention further provides a method of lubricating a mechanical device, typically a manual transmission with the lubricating composition. The invention further provides for the use of the lubricating composition to provide a number of benefits including lower operating temperatures and fuel economy.

Description

FIELD OF INVENTION[0001]The present invention relates to a lubricating composition containing (a) an oil of lubricating viscosity, (b) a star polymer and (c) a substantially linear polymer with a weight average molecular weight of 45,000 or less. The invention further provides a method of lubricating a mechanical device, typically a manual transmission with the lubricating composition. The invention further provides for the use of the lubricating composition to provide a number of benefits including lower operating temperatures and fuel economy.BACKGROUND OF THE INVENTION[0002]Viscosity index improvers are known to be added to lubricating oil compositions to improve the viscosity index of the lubricant. Typical viscosity index improvers include polymers of methacrylates, acrylates, olefins (such as copolymers of alpha-olefins and maleic anhydride and esterified derivatives thereof), or maleic anhydride-styrene copolymers, and esterified derivatives thereof. The viscosity index impro...

AI Technical Summary

Benefits of technology

[0008]The inventors of this invention have discovered that a lubricating composition, method and use as disclosed herein is capable of providing at least one of improved oxidative stability, reduced mechanical device operating temperatures, increased mechanical device durability, improved shear stability index, improved viscosity index, improved low temperature viscometrics and improved high temperature viscometrics.

[0028]In one embodiment the invention provides for the use of a lubricating composition as described herein to provide a lubricant (typically a manual transmission lubricant) with at least one (or at least two, or up to all) of acceptable or improved shear stability, acceptable or improved viscosity index control, acceptable or improved low temperature viscosity, acceptable or improved fuel economy, and acceptable or improved device operating temperatures. Typically the lubricant may be used in a driveline device such as a manual transmission.

Problems solved by technology

However, such viscosity index improvers have poor shear stability, too high a viscosity at low temperature, poor fuel economy, and poor non-dispersant cleanliness.

Conversely, higher viscosity fluids contribute to elevated gear and transmission operating temperatures, which are believed to reduce fuel economy and diminish durability.

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