Method of improving the acrylic rubber sealant compatibility in an internal combustion engine

A method of improving the acrylic rubber sealant compatibility in an internal combustion engine, said method comprising contacting the acrylic rubber sealant in the internal combustion engine and operating the internal combustion engine with a lubricating oil composition comprising:

• a) a major amount of a base oil of lubricating viscosity,
• b) a nitrogen-containing ashless dispersant in an amount of 0.01 to 0.3 wt. % in terms of the nitrogen content, based on the total amount of the lubricating oil composition,
• c) a metal-containing detergent of an alkali metal or alkaline earth metal salt of alkylphenol derivative having a Mannich base structure in an amount of 0.001 to 0.04 wt. % in terms of the metal content, based on the total amount of the lubricating oil composition, and
• d) a phosphorus-containing organic compound in an amount of 0.001 to 0.5 wt. % in terms of the phosphorus content, based on the total amount of the lubricating oil composition,
• wherein the ratio of components bi) to c) is in the range of from 1:0.005 to 1:2 in terms of the nitrogen content.