Lubricating oil composition with viscosity modifier with low shear stability index

Abstract

This disclosure describes a method of improving fuel economy of an engine. The method involves lubricating the engine with a lubricating oil composition that includes a) an oil of lubricating viscosity; and b) a viscosity modifier including an olefin copolymer or diene-based copolymer or homopolymer wherein the viscosity modifier has shear stability index of 15 or less. The lubricating oil composition is substantially free of viscosity modifiers other than the viscosity modifier of b).

What is claimed is: 
     
         1 . A method of improving fuel economy of an engine, the method comprising:
 lubricating the engine with a lubricating oil composition comprising:   a) an oil of lubricating viscosity; and   b) a viscosity modifier comprising an olefin copolymer or diene-based copolymer or homopolymer wherein the viscosity modifier has shear stability index of 15 or less;   wherein the lubricating oil composition is substantially free of viscosity modifiers other than the viscosity modifier of b).   
     
     
         2 . The method of  claim 1 , wherein the lubricating oil composition is substantially free of poly alkyl methacrylate (PMA) viscosity modifier. 
     
     
         3 . The method of  claim 1 , wherein the viscosity modifier is linear or star-shaped. 
     
     
         4 . The method of  claim 3 , wherein the star-shaped diene polymer has a weight average molecular weight of about 300,000 g/mol to 1,000,000 g/mol. 
     
     
         5 . The method of  claim 1 , wherein the olefin copolymer is an ethylene-propylene copolymer. 
     
     
         6 . The method of  claim 5 , wherein the ethylene-propylene based copolymer has a weight average molecular weight of about 10,000 g/mol to about 100,000 g/mol. 
     
     
         7 . The method of  claim 5 , wherein the ethylene-propylene based copolymer has an ethylene content of 35 to 70 wt % or 2 to 20 wt. % based on weight of the copolymer. 
     
     
         8 . The method of  claim 1 , wherein the diene-based copolymer or homopolymer is hydrogenated. 
     
     
         9 . The method of  claim 1 , wherein the viscosity modifier is a styrene hydrogenated diene copolymer. 
     
     
         10 . The method of  claim 1 , wherein the improvement in fuel economy is determined according to Fuel Economy Improvement (FEI) as measured from World Harmonized Transient Cycle or Heavy-Duty Supplemental Emissions Test modal mode dynamometer testing. 
     
     
         11 . A method of increasing the fuel economy of a diesel engine, the method comprising:
 lubricating the diesel engine with a lubricating oil composition comprising:   a) an oil of lubricating viscosity; and   b) a viscosity modifier comprising an olefin copolymer or diene-based copolymer or homopolymer, wherein the viscosity modifier has shear stability index of 15 or less;   
       wherein the lubricating oil composition is substantially free of viscosity modifiers other than the viscosity modifier of b). 
     
     
         12 . The method of  claim 11 , wherein the lubricating oil composition is substantially free of poly alkyl methacrylate (PMA) viscosity modifier. 
     
     
         13 . The method of  claim 11 , wherein the viscosity modifier is linear or star-shaped. 
     
     
         14 . The method of  claim 11 , wherein the viscosity modifier is an ethylene-propylene based copolymer. 
     
     
         15 . The method of  claim 11 , wherein the hydrogenated diene polymer has a weight average molecular weight of about 300,000 g/mol to 1,000,000 g/mol. 
     
     
         16 . The method of  claim 14 , wherein the ethylene-propylene based copolymer has a weight average molecular weight of about 10,000 g/mol to about 100,000 g/mol. 
     
     
         17 . The method of  claim 14 , wherein the ethylene-propylene based copolymer has an ethylene content of 35 to 70 wt % based on weight of the copolymer. 
     
     
         18 . The method of  claim 14 , wherein the ethylene-propylene based copolymer has an ethylene content of 2 to 20 wt % based on weight of the copolymer. 
     
     
         19 . The method of  claim 11 , wherein the hydrogenated diene polymer is a styrene hydrogenated diene copolymer. 
     
     
         20 . The method of  claim 11 , wherein the improvement in fuel economy is determined according to Fuel Economy Improvement (FEI) as measured from World Harmonized Transient Cycle or Heavy-Duty Supplemental Emissions Test modal mode dynamometer testing.