Lubricating oil composition and methods for controlling foam tendency and/or foam stability

Abstract

Provided is a lubricating oil composition and methods for controlling one or more of foam tendency and foam stability in such composition using as the oil a mixture of at least two base stocks. The at least two base stocks have a surface tension difference between them such that, when the surface tension difference is greater than 1.0 dynes/cm, then one or more of foam tendency and foam stability are enhanced as compared to foam tendency and foam stability achieved using the base stocks separately and not in the mixture. When the surface tension difference between them is less than 1.0 dynes/cm, then one or more of foam tendency and foam stability are reduced or equivalent as compared to foam tendency and foam stability achieved using the base stocks separately and not in the mixture. Two low-foaming base stocks can produce a significant high foam response that reduces or eliminates the need for pro-foaming additives.

Dependencies are inferred from the claim text.