Method of Reducing the Rate of Depletion of Basicity of a Lubricating Oil Composition in Use in an Engine

Abstract

Disclosed is a method of reducing the rate of depletion of basicity (as determined by ASTM D2896) of a lubricating oil composition in use in an engine. The lubricating oil composition includes at least one overbased alkali or alkaline earth metal detergent. The method comprises adding to the lubricating oil composition one or more compounds of Formula (I): wherein: x is 1 to 50, preferably 1 to 40, more preferably 1 to 30; R 1 and R 2 are H, hydrocarbyl groups having 1 to 12 carbon atoms, or hydrocarbyl groups having 1 to 12 carbon atoms and at least one heteroatom; R is a hydrocarbyl group having 9 to 100, preferably 9 to 70, most preferably, 9 to 50, carbon atoms; and n is 0 to 10, or alkaline earth metal salts thereof. The compounds of formula (I) are preferably methylene-bridged alkyl phenols or ethoxylated methylene-bridged alkyl phenols.

What is claimed is: 
     
         1 . A method of reducing the rate of depletion of basicity (as determined by ASTM D2896) of a lubricating oil composition in use in an engine, the lubricating oil composition including at least one oil-soluble overbased alkali or alkaline earth metal detergent, which method comprises adding to the lubricating oil composition one or more compounds of Formula (I): 
       
         
           
           
               
               
           
         
       
       wherein:
 x is 1 to 50, preferably 1 to 40, more preferably 1 to 30; 
 R 1  and R 2  are H, hydrocarbyl groups having 1 to 12 carbon atoms, or hydrocarbyl groups having 1 to 12 carbon atoms and at least one heteroatom; 
 R is a hydrocarbyl group having 9 to 100, preferably 9 to 70, most preferably, 9 to 50, carbon atoms; and 
 n is 0 to 10, or alkaline earth metal salts thereof. 
 
     
     
         2 . The method as claimed in  claim 1 , wherein n in Formula (I) is 0. 
     
     
         3 . The method as claimed in  claim 1 , wherein x in Formula (I) is 1. 
     
     
         4 . The method as claimed in  claim 1 , wherein R in Formula (I) is 9 to 20 carbon atoms. 
     
     
         5 . The method as claimed  claim 1 , wherein R in Formula (I) is branched. 
     
     
         6 . The method as claimed in  claim 1 , wherein R 1  is H, R 2  is H and R is in the para position in relation to the —O—[CH 2 CH 2 O] n H group in formula (I). 
     
     
         7 . The method as claimed in  claim 1 , wherein the compounds of formula (I) include less than 1 mole % of unreacted alkyl phenol. 
     
     
         8 . The method as claimed in  claim 1 , wherein n=1 for more than 60 mole % of the compounds of formula (I). 
     
     
         9 . The method as claimed in  claim 1 , wherein the alkaline earth metal salts of the compounds of Formula (I) are calcium or magnesium salts. 
     
     
         10 . The method as claimed  claim 1 , wherein compounds of formula (I) in which n≧2 constitute less than 5 mole % of the compounds of formula (I). 
     
     
         11 . The method as claimed in  claim 1 , wherein the compounds of formula (I) are methylene-bridged alkyl phenols or ethoxylated methylene-bridged alkyl phenols. 
     
     
         12 . The method as claimed in  claim 1 , wherein the lubricating oil composition has a TBN of 4 to 100 as measured by ASTM D2896. 
     
     
         13 . The method as claimed in  claim 1 , wherein the lubricating oil composition is a marine cylinder lubricant, a trunk piston engine oil, a gas engine oil or a crankcase lubricating oil composition.