Lubricating composition for use in diesel engines compatible with biofuel

Abstract

A method of operating a diesel engine comprises lubricating the diesel engine with a lubricating composition and using a biofuel as fuel, wherein the lubricating composition comprises a base oil belonging to Group III or Group II of the API base oil categories, from 0.5 to 5% by mass of a phenolic anti-oxidant, and from 0.5 to 5% by mass of an amine-based anti-oxidant, the total content of the anti-oxidants being at least 2% by mass.

What is claimed is: 
     
         1 . A method of operating a diesel engine comprising lubricating the diesel engine with a lubricating composition and using a biofuel as fuel, wherein the lubricating composition comprises a base oil belonging to Group III or Group II of the API base oil categories, from 0.5 to 5% by mass of a phenolic anti-oxidant and from 0.5 to 5% by mass of an amine-based anti-oxidant, the total content of the anti-oxidants being at least 2% by mass. 
     
     
         2 . The method according to  claim 1  wherein the phenolic anti-oxidant is a 6-methylheptyl alcohol ester of 3-(4-hydroxy-3,5-di-t-butyl-phenyl)propionic acid. 
     
     
         3 . The method according to  claim 1  wherein the amine-based anti-oxidant is a diphenylamine which is a reaction product of N-phenylbenzeneamine and 2,4,4-trimethylpentene. 
     
     
         4 . The method according to  claim 1  wherein the biofuel used in the diesel engine is derived from rapeseed oil. 
     
     
         5 . The method according to  claim 1  wherein the phenolic anti-oxidant is a 6-methylheptyl alcohol ester of 3-(4-hydroxy-3,5-di-t-butyl-phenyl)propionic acid and wherein the amine-based anti-oxidant is a diphenylamine which is a reaction product of N-phenylbenzeneamine and 2,4,4-trimethylpentene.