Alkali metal salts to minimize turbo sludge

Abstract

Turbo sludge formation is Improved in a turbo-charged, sump-lubricated internal combustion engine which is susceptible to contamination of lubricant with liquid fuel by providing said engine with a lubricant which contains an amount of an oil-soluble alkali metal salt effective to reduce the deterioration of said lubricant and said fuel contaminant.

1 . A method for lubricating a turbo-charged, sump-lubricated internal combustion engine with a lubricant, wherein the lubricant encounters a temperature within the turbocharger of at least about 300° C. wherein said lubricant is contaminated with liquid fuel, and wherein the lubricant is subject to deterioration as revealed by the formation of granular sediment, said method comprising providing said engine with a lubricant which contains an amount of an oil-soluble alkali metal salt effective to reduce the formatting of said granular sediment. 
     
     
         2 . The method of  claim 1  wherein the engine is a spark-ignited engine. 
     
     
         3 . (canceled) 
     
     
         4 . (canceled) 
     
     
         5 . The method of  claim 1  wherein said liquid fuel comprises greater than about 5 percent by weight content of cyclic materials boiling above about 150° C. 
     
     
         6 . The method of  claim 1  wherein said liquid fuel has a sulfur content of less than or equal to about 50 parts per million by weight. 
     
     
         7 . The method of  claim 1  wherein the alkali metal is lithium, sodium, or potassium. 
     
     
         8 . The method of  claim 1  wherein the alkali metal is sodium. 
     
     
         9 . The method of  claim 1  wherein the oil soluble alkali metal salt is a hydrocarbyl-substituted sodium sulfonate. 
     
     
         10 . The method of  claim 9  wherein the sodium sulfonate is overbased. 
     
     
         11 . The method of  claim 1  wherein the amount of the oil-soluble alkali metal salt is about 0.02 to about 2 percent by weight of the lubricant. 
     
     
         12 . The method of  claim 1  wherein the oil-soluble alkali metal salt provides about 0.004 to about 0.4 percent by weight alkali metal to the lubricant. 
     
     
         13 . The method of  claim 1  wherein the lubricant further comprises an aminic antioxidant or a rust inhibitor. 
     
     
         14 . The method of  claim 1  wherein the lubricant comprises at least about 0.5 percent by weight of an aminic antioxidant and less than about 2 percent by weight of a hindered phenolic antioxidant. 
     
     
         15 . The method of  claim 14  wherein the amount of aminic antioxidant in the lubricant is greater than the amount of the hindered phenolic antioxidant.