A method of passing the ASTM D6557 Ball Rust Test using a lubricating oil composition having a sulfated ash content of less than 1.0% by weight of the composition in which an oil-soluble hydrocarbyl phenol aldehyde condensate rust inhibitor of Formula (I) is added to the lubricating oil composition: wherein n is 0 to 10, Y is a divalent bridging group, and is preferably a hydrocarbyl group, preferably having from 1 to 4 carbon atoms; and R is a hydrocarbyl group having from 4 to 30 carbon atoms.