Lubricating oil compositions with improved friction properties

Abstract

The present invention concerns friction reducers for use in lubricating oil compositions which comprise certain groups of aromatic compounds, esters, narrow mixtures of base stocks, and/or amorphous polymers such as amorphous olefin copolymers. These compositions can provide substantial reductions in the coefficient of friction and fuel economy improving is benefits when admixed to lubricating oils without deleterious effects such as instability, undesirable high viscosities and deposits. In one aspect of the invention, pentaerythritol esters and optionally triol esters are added to lubricating oil compositions to provide reduced friction and improved fuel economy. In a second aspect of the invention, similar results are obtained by adding hydrocarbyl aromatics to a lubricating oil composition containing one or more of Groups II and III base stock. In a third aspect, the invention concerns a lubricating oil composition comprising an amorphous olefin copolymer and one or more of Groups II and III base stocks. In one embodiment, the third aspect also includes one or more of hydrocarbyl aromatics and polyol esters as part of the composition. In a forth aspect, moderate concentrations of hydrocarbyl aromatics are used in a lubricating oil composition comprising paraffinic base oil stocks and preferably a borated polyisobutenyl succinimide ashless dispersant.

1 . A method of improving fuel economy of an internal combustion engine by lubricating the engine with a lubricant composition selected from the group of lubricants consisting of: 
 (i) a lubricant composition comprising (a) a mixture of about 3 wt % to about 30 wt % pentaetydiritol esters in a base stock wherein said lubricating composition contains more than about 18 wt % saturates; (b) 0 to 2 wt % of at least one triol ester; (c) 0 to about 3.3 wt % of a borated hydrocarbyl succinimide (active ingredient) and wherein the percentages are based upon the total lubricating composition;    (ii) a lubricant composition comprising (a) about at least 20 wt % of one or more base stocks selected from the group consisting of Group II base stocks, Group III base stocks, and wax isomerates; (b) about at least 4 wt % of a hydrocarbyl aromatic; (c) 0 to 3.3 wt % of a borated hydrocarbyl succinimide (active ingredient), and wherein the percentages are based upon the total lubricating composition; and,    (iii) a lubricant composition comprising (a) one or more base stocks selected from the group consisting of Group II base stock, Group III base stocks and wax isomerates; (b) an amorphous olefin copolymer; and (c) 0 to 3.3 wt % of a borated hydrocarbyl succinimide.    
     
     
         2 . The method of  claim 1  wherein lubricant (i) contains at least 20 wt % of a base stock containing at least 90% saturates.  
     
     
         3 . The method of  claim 1  wherein a lubricant (i) comprises a GTL base stock.  
     
     
         4 . The method of  claim 1  wherein lubricant (iii) comprises at least one member selected from the group consisting of esters, hydrocarbyl aromatics and mixtures thereof.  
     
     
         5 . The method of  claim 4  wherein said member comprises about 1 wt % to about 30 wt % of the lubricating compositions.  
     
     
         6 . The method of  claim 1  wherein the hydrocarbyl group of said borated hydrocarbyl succinimide has an M n  from about 1000 to about 5000.  
     
     
         7 . The method of  claim 6  wherein said borated hydrocarbyl succinimide is a borated polyisobutenyl succinimide.  
     
     
         8 . The method of  claim 7  wherein said borated polyisobutenyl succinimide contains both mono and bis succinimide.