Lubricating composition

Abstract

Lubricating composition for use in the crankcase of an engine comprising: (i) a base oil comprising at least one monoester or a mixture of monoesters, wherein said monoester or mixture of monoesters has a kinematic viscosity at 100° C. of not more than 4 mm 2 /s, a viscosity index of at least 130 and a Noack evaporation loss of not more than 20 wt %; and (ii) a polymeric viscosity index improvers selected from (a) one or more comb polymers; (b) a poly(meth)acrylate polymer having 1 to 70 mol % of one or more (meth)acrylate structural units represented by formula (1) below (1) wherein R 1 is a hydrogen atom or a methyl group, and R 2 is a straight chain or branched hydrocarbon group having not less than 16 carbon atoms; (c) styrene-diene hydrogenated copolymers; and (d) mixtures thereof. The lubricating composition of the present invention provides improved fuel economy properties.

1 . A lubricating composition for use in the crankcase of an engine comprising:
 (i) a base oil comprising at least one monoester or a mixture of monoesters, wherein said monoester or mixture of monoesters has a kinematic viscosity at 100° C. of not more than 4 mm 2 /s, a viscosity index of at least 130 and a Noack evaporation loss of not more than 20 wt %; and   (ii) a polymeric viscosity index improver selected from
 (a) one or more comb polymers; 
 (b) a poly (meth) acrylate polymer having 1 to mol % of one or more (meth) acrylate structural units represented by formula (1) below 
   
       
         
           
           
               
               
           
         
         
           
             wherein R 1  is a hydrogen atom or a methyl group, and R 2  is a straight chain or branched hydrocarbon group having not less than 16 carbon atoms; 
           
           (c) styrene-diene hydrogenated copolymers; and 
           (d) mixtures thereof. 
         
       
     
     
         2 . A lubricating composition according to  claim 1  wherein said monoester or mixtures of monoesters has a kinematic viscosity at 100° C. of not more than 3.3 mm 2 /s. 
     
     
         3 . A lubricating composition according to  claim 1  wherein said monoester or mixtures of monoesters has a Noack evaporation loss of not more than 15 wt %. 
     
     
         4 . A lubricating composition according to  claim 1  wherein the at least one monoester or mixture of monoesters is present at a total level of at least 10 wt %, by weight of the lubricating composition. 
     
     
         5 . A lubricating composition according to  claim 1  wherein the at least one monoester or mixture of monoesters is present at a total level of at most 75 wt %, by weight of the lubricating composition. 
     
     
         6 . A lubricating composition according to  claim 1  wherein the polymeric viscosity index improver is a comb polymer. 
     
     
         7 . A lubricating composition according to  claim 1  wherein the polymeric viscosity index improver is present in a solid polymer amount of from 0.1 wt % to 7 wt %, by weight of the lubricating composition. 
     
     
         8 . A lubricating composition according to  claim 1  wherein said at least one monoester or mixture of said monoesters has a non-polarity index of at least 90. 
     
     
         9 . A lubricating composition according to  claim 1  wherein said at least one monoester or mixture of said monoesters has a pour point of not more than −30° C. 
     
     
         10 . A lubricating composition according to  claim 1  wherein said at least one monoester, or mixture of said monoesters has a kinematic viscosity at 100° C. of not more than 3.0 cSt and/or a viscosity index of at least 140 and/or a pour point of not more than −35° C. and/or a Noack evaporation loss of not more than 15.0 wt %. 
     
     
         11 . A lubricating composition according to  claim 1  wherein said at least one monoester is the reaction product of a monohydric alcohol and a monocarboxylic acid wherein said monohydric alcohol is at least one saturated branched-chain aliphatic monohydric alcohol having between 16 and 36 carbon atoms and wherein said monocarboxylic acid is at least one saturated straight-chain aliphatic monocarboxylic acid having between 5 and 10 carbon atoms. 
     
     
         12 . A lubricating composition according to  claim 11  wherein said alcohol comprises an alcohol branched at the β position on the main carbon chain and which contains 20 carbon atoms. 
     
     
         13 . A lubricating composition according to  claim 11  wherein said acid is pentanoic acid and/or heptanoic acid. 
     
     
         14 . A lubricating composition according to  claim 1  wherein the base oil additionally comprises a Fischer-Tropsch derived base oil. 
     
     
         15 . A method comprising:
 applying a lubricating composition according to  claim 1  to a surface in the crankcase of an engine.