Method of Lubricating an Internal Combustion Engine

Abstract

The present invention relates to a method of lubricating an internal combustion engine with a power output of at least 1600 kilowatts by supplying to the internal combustion engine a lubricating composition containing an oil of lubricating viscosity and at least 0.5 wt % of a hydrocarbyl-substituted carboxylic acid or anhydride thereof. The invention further provides a lubricating composition suitable for the method.

1 . A method of lubricating a 2-stroke internal combustion engine cylinder liner comprising supplying to the internal combustion engine a lubricating composition comprising (a) an oil of lubricating viscosity and (b) at least 0.5 wt % to 20 wt % of a carboxylic acid or an anhydride thereof, wherein the carboxylic acid or anhydride thereof has a hydrocarbyl group of at least about 10 carbon atoms. 
     
     
         2 . The method of  claim 1  wherein the hydrocarbyl group of the carboxylic acid or anhydride thereof has number average molecular weight of 450 to 20,000. 
     
     
         3 . The method of  claim 1  wherein the hydrocarbyl group of the carboxylic acid or anhydride thereof has number average molecular weight of 450 to 1500, and wherein the carboxylic acid or anhydride thereof is present at 2 to 20 wt % of the lubricating composition. 
     
     
         4 . The method of  claim 1  wherein the hydrocarbyl group of the carboxylic acid or anhydride thereof has number average molecular weight of greater than 1500 to 5000, and wherein the carboxylic acid or anhydride thereof is present at 0.5 to less than 10 wt % of the lubricating composition. 
     
     
         5 . The method of  claim 1  wherein the carboxylic acid or anhydride thereof is a polyisobutylene-substituted succinic acid or anhydride. 
     
     
         6 . The method of  claim 1  wherein the lubricating composition has a SAE 40 viscosity or SAE 50 viscosity. 
     
     
         7 . The method of  claim 1  wherein the lubricating composition has 0 to less than 15 wt % of bright stock. 
     
     
         8 . The method of  claim 1  wherein the lubricating composition contains 0 to less than 3 wt % of a dispersant. 
     
     
         9 . The method of  claim 1  wherein the lubricating composition contains 0 to less than 15 wt % of bright stock; and 0 to 2 wt % of a dispersant. 
     
     
         10 . The method of  claim 1  wherein the lubricating composition further comprises at least one detergent selected from the group consisting of sulphonates, salicylates, salixarates, phenates, hybrid salicylate-phenate compositions, hybrid phenate-stearate compositions and hybrid sulphonate-phenate compositions. 
     
     
         11 . The method of  claim 1 , wherein the 2-stroke internal combustion engine is a marine diesel engine or a stationary power engine. 
     
     
         12 . A method of lubricating a 2-stroke internal combustion engine cylinder liner comprising supplying to the internal combustion engine a lubricating composition comprising (a) an oil of lubricating viscosity and (b) at least 0.5 wt % to 20 wt % of a carboxylic acid or an anhydride thereof, wherein the carboxylic acid or anhydride thereof has a hydrocarbyl group of at least about 10 carbon atoms, and (c) at least 5 wt % of an overbased sulphonate detergent. 
     
     
         13 . A method of reducing the amount of bright stock in a lubricating composition used in lubricating a 2-stroke internal combustion engine cylinder liner, comprising supplying to the internal combustion engine a lubricating composition comprising (a) an oil of lubricating viscosity and (b) at least 0.5 wt % to 20 wt % of a carboxylic acid or an anhydride thereof, wherein the carboxylic acid or anhydride thereof has a hydrocarbyl group of at least about 10 carbon atoms.