Patent ID: 8748357

Claim:
A method for controlling the oxidation of diesel engine lubricating oils caused by the use of biodiesel fuels in the diesel engine, said method comprising the addition to the lubricating oil of an additive comprising a premixed mixture of: (A) a first antioxidant selected from a hindered phenol antioxidant, wherein the hindered phenol antioxidant is 4,4′-methylene-bis (2,6-di-t-butyl phenol) at a loading of about 0.35 wt %; (B) a second antioxidant selected from a diphenyl amine antioxidant, wherein the diphenyl amine antioxidant is alkyl diphenylamine having alkyl substituted group(s) of at least 6 carbon atoms at a loading of about 0.35 wt %; and (C) a third catalytic antioxidant including molybdenum dithiocarbamate at a loading of about 0.1 wt %, and optionally ZnDDP at a loading of about 0.2 wt %; and, (D) wherein the premixed mixture is prepared by combining (A), (B) and (C) in the absence of any solvent or diluent, and mixing with stirring at a temperature of about 50° C. from 30 to 40 minutes, wherein the lubricating oil is a formulated 5W30 engine oil including 3 wt % of soy methyl ester.