Method of operating internal combustion engine by introducing antioxidant into combustion chamber

Abstract

In a method of operating an internal combustion engine, an antioxidant composition is introduced into a combustion chamber of the engine. The antioxidant composition contains (A) a sterically hindered phenol; (B) an alkylene or alkylidene coupled sterically hindered phenol oligomer; (C) a secondary aromatic amine; (D) a reaction product of a hydrocarbyl-substituted hydroxy-containing aromatic compound, an aldehyde, and a carboxyl-substituted phenol; or (E) a mixture thereof. The method improves the performance of a lubricating oil of the engine.

1 . A method of operating an internal combustion engine, comprising: introducing an antioxidant composition comprising 
 (A) a sterically hindered phenol;    (B) an alkylene or alkylidene coupled sterically hindered phenol oligomer;    (C) a secondary aromatic amine;    (D) a reaction product of a hydrocarbyl-substituted hydroxy-containing aromatic compound, an aldehyde, and a carboxyl-substituted phenol; or    (E) a mixture thereof into a combustion chamber of the engine during the operation of the engine.    
     
     
         2 . The method of  claim 1  wherein the antioxidant composition is essentially free of sulfur and phosphorus.  
     
     
         3 . The method of  claim 1  wherein the antioxidant composition is introduced into the combustion chamber by injection from a dosing system or as a component of a fuel composition.  
     
     
         4 . The method of  claim 3  wherein the antioxidant composition is present in the fuel composition at 0.1 to 40,000 ppm by weight.  
     
     
         5 . The method of  claim 1  wherein the antioxidant composition (A) is a phenol having two or more alkyl substituents that contain 1 to 24 carbon atoms and that occupy the 2-position and 6-position of the phenolic ring.  
     
     
         6 . The method of  claim 1  wherein the antioxidant composition (B) is a methylene coupled phenol oligomer containing two or more phenolic rings wherein each phenolic ring is occupied at the 2-, 4- and 6-positions by an alkyl or arylalkyl group.  
     
     
         7 . The method of  claim 1  wherein the antioxidant composition (C) is a diarylamine containing one or more alkyl substituents wherein each substituent contains up to 16 carbon atoms.  
     
     
         8 . The method of  claim 1  wherein the antioxidant composition (D) is the reaction product of an alkylphenol, formaldehyde, and salicylic acid.  
     
     
         9 . The method of  claim 1  wherein the antioxidant further comprises one or more fuel additives.  
     
     
         10 . A method of improving the performance of a lubricating oil of an internal combustion engine by operating the engine according to the method of  claim 1 .  
     
     
         11 . The method of  claim 10  wherein the engine is a compression-ignited engine or spark-ignited direct injection engine having an exhaust gas recirculation system.  
     
     
         12 . The method of  claim 10  wherein the engine is a compression-ignited or spark-ignited engine having an exhaust treatment device, and the lubricating oil has at least one of the properties selected from the group consisting of a phosphorus content below 0.1% by weight, a sulfur content below 0.5% by weight, and a sulfated ash content below 1.5% by weight.  
     
     
         13 . The method of  claim 10  wherein the engine is installed on a motor vehicle and has a recommended drain interval for the lubricating oil of the engine of greater than 6,000 miles.  
     
     
         14 . The method of  claim 10  wherein the engine is a stationary engine having a recommended drain interval for the lubricating oil of the engine of greater than 150 operational hours.  
     
     
         15 . The method of  claim 10  wherein the engine is a compression-ignited or spark-ignited engine having an exhaust treatment device, and a fuel of a fuel composition used to fuel the engine has a sulfur content below 80 ppm by weight.