Sulfurized-Olefin Oxidation Inhibitors for Lubricating Oils

Lubricating oil compositions comprising an effective amount of a sulfurized olefin oxidation inhibitor containing two or fewer sulfur atoms in the sulfur bridge provide improved oxidative oil thickening in internal combustion engines as demonstrated in the Sequence IIIF test.

The present invention relates to lubricating oil compositions containing sulfurized olefin oxidation inhibitors.� More particularly, lubricating oil compositions of the present invention provide improved oxidative oil thickening in internal combustion engines when an effective amount of the sulfurized olefin oxidation inhibitor is incorporated in the lubricating oil compositions.

The Sequence III test has been completely redesigned for API SL/ILSAC GF-3 as the Sequence IIIF.� The new API SL/ILSAC GF-3 passenger car engine oil category places a premium on oxidative oil thickening.� In particular, the Sequence IIIF engine dynamometer test is specifically designed to severely stress engine oils under high-speed, high-load conditions for 80 hours of continuous operation.� Oxidation control has proven to be a significant challenge.� Traditional oxidation inhibitors or inhibitor combinations are largely ineffective in the Sequence IIIF.� The Sequence IIIF uses a different engine, unleaded fuel, longer test time, and fewer oil additions than previous Sequence III tests.� Together, these changes produce a more severe oxidation test.

Sulfurized olefins have been found to control oxidative oil thickening, i.e., viscosity increase, in the Sequence IIIF.� For example, a commercially available sulfurized olefin marketed by Chevron Oronite Chemical Company adequately controls Sequence IIIF oxidative oil thickening.�

This publication summarizes work performed with sulfurized olefins that will deliver adequate oxidation control when employed in lubricating oil compositions in internal combustion engines.

As mentioned above, the present invention provides improved oxidative oil thickening in internal combustion engines when an effective amount of sulfurized olefin oxidation inhibitor is incorporated in the lubricating oil composition.

The present invention comprises a base oil of lubricating viscosity and an effective amount of a sulfurized olefin to reduce oxidative thickening of a lubricating oil composition when used in an internal combustion engine.

The lubricant compositions of the present invention include a major amount of base oil of lubricating viscosity.� Base oil as used herein is defined as a base stock or blend of base stocks which is a lubricant component that is produced by a single manufacturer to the same specifications (independent of feed source or manufacturer’s location) that meets the same manufacturer’s specification; and that is identified by a unique formula, product identification number...