Method for improving elastomer compatibility

Abstract

This invention relates to a method of improving elastomer seal compatibility and dispersancy in an internal combustion engine by contacting the elastomer seal in the internal combustion engine with a lubricating oil composition comprising: a) a major amount of a base oil of lubricating viscosity; b) a carboxylated detergent-dispersant obtained by: (i) neutralizing alkylphenols using an alkaline earth base in the presence of at least one carboxylic acid that contains from one to four carbon atoms but in the absence of alkali base, dialcohol, and monoalcohol, forming an intermediate product; and (ii) carboxylating the intermediate product using carbon dioxide so that at least 20 mole percent of the original alkylphenol starting material has been converted to alkaline earth metal single aromatic-ring hydrocarbyl salicylate; and c) a nitrogen-containing dispersant.

Dependencies are inferred from the claim text.