Method of Viscosity Control

Abstract

This invention relates to a method of lubricating an internal combustion engine comprising at least one of a crankcase, a gear and a wet-clutch, said method comprising supplying to said crankcase, gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from 1000 to 75,000, wherein the lubricating composition has a SAE viscosity grade from XW-Y, wherein X is from 0 to 20 and Y is from 20 to 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

1 . A method of lubricating an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of said gear and wet-clutch a lubricating composition comprising:
 (a) an oil of lubricating viscosity; and   (b) a viscosity modifier with a number average molecular weight from about 1000 to about 75,000,   wherein the lubricating composition has a SAE viscosity grade from XW-Y, wherein X is from 0 to about 20 and Y is from about 20 to about 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less, wherein the internal combustion engine is a 4-stroke motorcycle engine.   
   
   
       2 . The method of  claim 1 , wherein the internal combustion engine has a common oil reservoir supplying the same lubricating composition to the crankcase and at least one of a gear and a wet-clutch. 
   
   
       3 . The method of  claim 1 , wherein the lubricating composition is supplied to the crankcase and to the gear (or multiplicity of gears). 
   
   
       4 . The method of  claim 1 , wherein the lubricating composition is supplied to the crankcase and the wet clutch. 
   
   
       5 . The method of  claim 1 , wherein the lubricating composition is supplied to the crankcase and both the gear (or gears) and the wet clutch. 
   
   
       6 . The method of  claim 1 , wherein the viscosity modifier includes at least one of:
 (a) polyalkenes or a derivative thereof;   (b) polyalphaolefins;   (c) alpha-olefin-unsaturated carboxylic reagent copolymers;   (d) poly(meth)acrylates;   (e) Esterified interpolymers derived from the polymerisation of a vinyl aromatic monomer and an unsaturated carboxylic acid; or   (f) mixtures thereof.   
   
   
       7 . The method of  claim 1 , wherein the viscosity modifier has a number average molecular weight 2000 to 60,000, or 8000 to 40,000. 
   
   
       8 . The method of  claim 1 , wherein the viscosity modifier has a number average molecular weight from 1000 to 20,000, or from 25,000 to 40,000. 
   
   
       9 . The method of  claim 1 , wherein the viscosity modifier is a poly(meth)acrylate. 
   
   
       10 . The method of  claim 9 , wherein the viscosity modifier is a functionalized poly(meth)acrylate. 
   
   
       11 . The method of  claim 10 , wherein the poly(meth)acrylate is functionalized with a nitrogen containing monomer. 
   
   
       12 . The method of  claim 1 , wherein the viscosity modifier is present from 0.5 wt % to 95 wt %, or from 1 wt % to 40 wt % of the lubricating composition. 
   
   
       13 . The method of  claim 1 , wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 22 or less. 
   
   
       14 . The method of  claim 1 , wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 4 to 18. 
   
   
       15 . A method of lubricating a 4-stroke motorcycle internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of said gear and wet-clutch a lubricating composition comprising:
 (a) an oil of lubricating viscosity; and   (b) a poly(meth)acrylate viscosity modifier with a number average molecular weight from about 1000 to about 75,000,   wherein the lubricating composition has an SAE viscosity grade from XW-Y, wherein X is from 0 to about 20 and Y is from about 20 to about 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.