Lubricating oil compositions

Abstract

A lubricating oil composition having a sulphated ash content of less than or equal to 1.2 mass % as determined by ASTM D874 and a phosphorous content of less than or equal to 0.12 mass % as determined by ASTM D5185, which lubricating oil composition comprises or is made by admixing: an oil of lubricating viscosity, in a major amount; an oil-soluble or oil-dispersible polymeric friction modifier as an additive in an effective minor amount; and, an oil-soluble or oil-dispersible dihydrocarbyl dithiophosphate metal salt as an additive in an effective minor amount.

What is claimed is: 
     
         1 . A lubricating oil composition having a sulphated ash content of less than or equal to 1.2 mass % as determined by ASTM D874 and a phosphorous content of less than or equal to 0.12 mass % as determined by ASTM D5185, which lubricating oil composition comprises or is made by admixing:
 (A) an oil of lubricating viscosity, in a major amount;   (B) an oil-soluble or oil-dispersible polymeric friction modifier as an additive in an effective minor amount, the polymeric friction modifier being the reaction product of solely:
 (i) a functionalised polyolefin; 
 (ii) a polyalkylene glycol; 
 (iii) a polyol; and, 
 (iv) a polycarboxylic acid; 
   and,   (C) at least one oil-soluble or oil-dispersible dihydrocarbyl dithiophosphate metal salt as an additive in an effective minor amount.   
     
     
         2 . A composition as claimed in  claim 1 , wherein the functionalised polyolefin (B (i)) is a functionalised polyisobutylene. 
     
     
         3 . A composition as claimed in  claim 1 , wherein the functionalised polyolefin (B (i)) is functionalised with a diacid or anhydride functional group. 
     
     
         4 . A composition as claimed in  claim 2 , wherein the functionalised polyolefin (B (i)) is functionalised with a diacid or anhydride functional group. 
     
     
         5 . A composition as claimed in  claim 3 , wherein the functionalised polyolefin (B (i)) is functionalised with a succinic anhydride functional group. 
     
     
         6 . A composition as claimed in  claim 4 , wherein the functionalised polyolefin (B (i)) is functionalised with a succinic anhydride functional group. 
     
     
         7 . A composition as claimed in  claim 1 , wherein the functionalised polyolefin (B (i)) is polyisobutylene succinic anhydride (PIBSA). 
     
     
         8 . A composition as claimed in  claim 1 , wherein the polyalkylene glycol is a poly(C 2  to C 6  alkylene) glycol. 
     
     
         9 . A composition as claimed in  claim 8 , wherein the polyalkylene glycol is polyethylene glycol (PEG). 
     
     
         10 . A composition as claimed in  claim 1 , wherein the polyol is a C 2  to C 20  aliphatic hydrocarbyl polyol. 
     
     
         11 . A composition as claimed in  claim 10 , wherein the C 2  to C 20  aliphatic hydrocarbyl polyol is glycerol. 
     
     
         12 . A composition as claimed in  claim 1 , wherein the polycarboxylic acid is a C 2  to C 20  aliphatic hydrocarbyl dicarboxylic acid. 
     
     
         13 . The composition as claimed in  claim 12 , wherein the C 2  to C 20  aliphatic hydrocarbyl dicarboxylic acid is sebacic acid. 
     
     
         14 . The composition as claimed in  claim 1 , wherein the oil-soluble or oil-dispersible dihydrocarbyl dithiophosphate metal salt is a zinc dihydrocarbyl dithiophosphate. 
     
     
         15 . A method of lubricating a spark-ignited or compression-ignited internal combustion engine comprising lubricating the engine with a lubricating oil composition as claimed in  claim 1 .