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 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 lubricating composition comprising a mixture of: 
 (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, and    (b) about at least 4 wt % of a hydrocarbyl aromatic    wherein the percentages are based upon the total lubricating composition.    
   
   
       2 . A lubricating composition of  claim 1  including a borated hydrocarbyl succinimide wherein the hydrocarbyl group has a M n  of about 1000 to about 5000. 
 wherein the percentages are based upon the total lubricating composition.    
   
   
       3 . A lubricating composition of  claim 2  wherein said borated hydrocarbyl succinimide is a borated polyisobutenyl succinimide and is provided at about 0.3 wt % active to about 3.3 wt % active.  
   
   
       4 . A lubricating composition of  claim 3  including: 
 (a) at least about 40% one or more base stocks selected from the group consisting of Group II base stocks, Group III base stocks, and wax isomerates,    (b) at least about 20% hydrocarbyl aromatic, and    (c) an ashless dispersant providing about 2 wt % active borated polyisobutenyl succinimide.    
   
   
       5 . A lubricating composition of  claim 3  comprising about 20 wt % to about 60 wt % of one or more of said base stocks.  
   
   
       6 . A lubricating composition as in claims  3 ,  4  or  5  wherein said borated polyisobutenyl succinimide comprises borated polyisobutenyl mono- and bis-succinimides.