NOVELTY - Lubricating oil composition comprises or contaminated with at least about 0.1 wt.% of a biodiesel fuel or its decomposition product, based on the total weight of the lubricating oil composition, the lubricating composition further comprises an oil of lubricating viscosity and about 0.05 to about 8 weight percent of an antioxidant which comprises an alkylene-coupled phenol; an alkyl group which is hydrocarbyl-substituted in the 1 and/or 2 position, located in a position ortho to the hydroxy group of the phenol unit; and an alkylene linking group in the other ortho position of the phenol unit.    USE - The lubricating oil composition is useful for lubricating diesel engine fueled with liquid fuel containing at least about 2 percent by weight of fatty acid alkyl ester (claimed).    ADVANTAGE - Use of the alkylene-coupled phenol compound is provided to reduce corrosion and oxidative instability resulting from biodiesel introduction into the lubricant.    DETAILED DESCRIPTION - Lubricating oil composition comprises or contaminated with at least about 0.1 wt.% of a biodiesel fuel or its decomposition product, based on the total weight of the lubricating oil composition, the lubricating composition further comprising an oil of lubricating viscosity and about 0.05 to about 8 weight percent of an antioxidant which comprises an alkylene-coupled phenol, where the alkylene-coupled phenol comprises at least two phenol units, at least one phenol unit having a hydrocarbyl substituent in the position para to the hydroxy group of the phenol unit; an alkyl group which is hydrocarbyl-substituted in the 1 and/or 2 position, located in a position ortho to the hydroxy group of the phenol unit; and an alkylene linking group in the other ortho position of the phenol unit. An INDEPENDENT CLAIM is included for a method for lubricating a diesel engine fueled with a liquid fuel containing at least about 2 percent by weight of a fatty acid alkyl ester, involving supplying to the engine a lubricant comprising an oil of lubricating viscosity and about 0.05 to about 8 weight percent of an antioxidant which comprises an alkylene-coupled phenol, where the alkylene-coupled phenol comprises at least two phenol units, at least one phenol unit having a hydrocarbyl substituent in the position para to the hydroxy group of the phenol unit; an alkyl group which is hydrocarbyl-substituted in the 1 and/or 2 position, located in a position ortho to the hydroxy group of the phenol unit; and an alkylene linking group in the other ortho position of the phenol unit.