Lubricant oil composition

Abstract

Provided is a lubricating oil composition favorable for reducing friction in a sliding mechanism equipped with a piston ring and a liner, in a device having the sliding mechanism. The lubricating oil composition contains a lubricant base oil, (1) a polymethacrylate and/or an olefin copolymer having a mass-average molecular weight of 100,000 to 600,000, and (2) an ester-type ashless friction modifier and/or an amine-type ashless friction modifier, and has a shear viscosity at 150° C. of 2.3 mPa· or more and less than 3.7 mPa·s.

1 . A lubricating oil composition for use in a device having a sliding mechanism equipped with a piston ring and a liner, which comprises a lubricant base oil, (1) a polymethacrylate and/or an olefin copolymer having a mass-average molecular weight of 100,000 to 600,000, and (2) an ester-type ashless friction modifier and/or an amine-type ashless friction modifier, and has a shear viscosity at 150° C. of 2.3 mPa·s or more and less than 3.7 mPa·s. 
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the mass-average molecular weight of the polymethacrylate and/or the olefin copolymer (1) is 200,000 to 550,000. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the content of the polymethacrylate and/or the olefin copolymer (1) is 2.5% by mass or more and less than 15% by mass based on the total amount of the composition. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the content of the ashless friction modifier is 0.1% by mass or more and less than 2% by mass based on the total amount of the composition. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the viscosity index of the lubricant base oil is 120 or more. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the phosphorus content is 0.12% by mass or less based on the total amount of the composition. 
     
     
         7 . The lubricating oil composition according to  claim 1 , which contains a Ca-containing metallic detergent and/or a Mg-containing metallic detergent in an amount of 0.05% by mass or more and 0.30% by mass or less as a total amount of Ca and Mg based on the total amount of the composition. 
     
     
         8 . The lubricating oil composition according to  claim 1 , which comprises polybutenylsuccinic imide and/or a boronated polybutenylsuccinic imide. 
     
     
         9 . The lubricating oil composition according to  claim 1 , which is for internal combustion engines. 
     
     
         10 . The lubricating oil composition according to  claim 1 , wherein the piston ring in a sliding mechanism equipped with a piston ring and a liner is one treated with chromium nitride. 
     
     
         11 . A method for producing the lubricating oil composition of  claim 1 , which comprises a step of blending a lubricant base oil with (1) a polymethacrylate and/or a olefin copolymer having a mass-average molecular weight of 100,000 to 600,000 stated above and (2) an ester-type ashless friction modifier and/or an amine-type ashless friction modifier stated above. 
     
     
         12 . A method of lubricating a device having a sliding mechanism equipped with a piston ring and a liner, which comprises lubricating a device having a sliding mechanism equipped with a piston ring and a liner with the lubricating oil composition of  claim 1 .