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 about 3 wt % to about 30 wt % pentaerythritol esters in a base stock wherein said lubricating composition contains more than about 18 wt % saturates and wherein the percentages are based upon the total lubricating composition.  
   
   
       2 . A lubricating composition as in  claim 1  wherein the composition contains at least 20 wt % of a base stock having at least 90% saturates wherein the percentages are based upon the total lubricating composition.  
   
   
       3 . A lubricating composition as in  claim 1  wherein said base stock is a GTL base stock.  
   
   
       4 . A lubricating composition as in  claim 1  including at least one triol ester.  
   
   
       5 . A lubricating composition as in  claim 4  wherein said base stock includes at least 90% saturates.  
   
   
       6 . A lubricating composition as in any one of the claims  4  or  5  wherein said triol esters are provided at about at least 2 wt %.  
   
   
       7 . A lubricating composition as in  claim 6  wherein said base stock is a GTL base stock.  
   
   
       8 . A lubricating composition as in  claim 1  including a borated hydrocarbyl-substituted succinimide wherein the hydrocarbyl group has a M n  from about 1000 to about 5000.  
   
   
       9 . A lubricating composition as in  claim 8  wherein said borated polyisobutenyl succinimide is provided at about at least 0.3 wt % active to about 3.3 wt % active.  
   
   
       10 . A lubricating composition as in  claim 9  where said borated isobutenyl succinimide comprises both mono and bis succinimides.