Low ash lubricating compositions for controlling steel corrosion

A low-ash lubricating oil composition suitable for use in lubricating the engine of a passenger car, the low-ash lubricating oil composition including

• one or more base oils of lubricating viscosity;
• a total calculated sulfated ash (SASH) of about 0.5 weight percent or less;
• about 0.02 to about 0.3 weight percent of an acyclic corrosion inhibitor including one or more oil-soluble acids, diacids, acid-esters, or combinations thereof having a C6 or greater hydrocarbyl chain and being substantially free of compounds having imine, imide, amidine structural units or hydroxy derivatives thereof, wherein the acyclic corrosion inhibitor is a blend of an oil-soluble diacid and an oil-soluble acid-ester each having the structure of Formula I:
• wherein
• each of R1 and R2 is, independently, selected from —OH or —OR4OH with at least one of R1 and R2 being-OH;
• R3 is a linear or branched C10 to C12 hydrocarbyl group;
• R4 is a linear or branched C1 to C4 hydrocarbyl group with the —OH thereof being a primary or secondary alcohol;
• wherein the lubricating oil composition is substantially free of a metal dialkyldithiophosphate;
• and
• wherein the lubricating oil composition exhibits a stable emulsion at 0° C. and/or 25° C. pursuant to the E85 emulsion test of ASTM D7563 and no steel corrosion pursuant to the humidity corrosion test of GMW 16073.