Low viscosity gear oil composition providing enhanced fuel efficiency

Abstract

A gear oil composition includes base oil including poly-alpha-olefin (PAO) synthetic oil in 70 to 95% by weight and oil-soluble polyalkylene glycol (OSP) synthetic oil in 5 to 30% by weight based on the weight of the base oil. The gear oil further includes a polyalkyl methacrylate-based Viscosity modifer in 5 to 20 parts by weight, based on 100 parts by weight of the base oil.

What is claimed is: 
     
         1 . A gear oil composition comprising:
 base oil including poly-alpha-olefin (PAO) synthetic oil in 70 to 95% by weight and oil-soluble polyalkylene glycol (OSP) synthetic oil in 5 to 30% by weight based on the weight of the base oil; and   a polyalkyl methacrylate-based Viscosity modifer in 5 to 20 parts by weight, based on 100 parts by weight of the base oil.   
     
     
         2 . The gear oil composition of  claim 1 , further comprising:
 additives in 3 to 20 parts by weight, based on 100 parts by weight of the base oil.   
     
     
         3 . The gear oil composition of  claim 1 , wherein the poly-alpha-olefin (PAO) synthetic oil has an average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 or greater, and a pour point of −50° C. or lower. 
     
     
         4 . The gear oil composition of  claim 1 , wherein the oil-soluble polyalkylene glycol (OSP) synthetic oil has an average kinematic viscosity of 6 to 12 cSt at 100° C., a viscosity index of 140 or greater, and a pour point of −40° C. or lower. 
     
     
         5 . The gear oil composition of  claim 1 , wherein the polyalkyl methacrylate-based Viscosity modifer has a kinematic viscosity of 650 cSt or greater at 100° C. 
     
     
         6 . The gear oil composition of  claim 1 , wherein the polyalkyl methacrylate-based Viscosity modifer has a number average molecular weight range of 300,000 to 400,000, and has 4 to 10 C 12  to C 15  polymer chains. 
     
     
         7 . The gear oil composition of  claim 6 , wherein the C 12  to C 15  polymer chains include alkyl methacrylate in 60 to 80% by weight and 2-ethylhexyl methacrylate in 20 to 40% by weight. 
     
     
         8 . The gear oil composition of  claim 2 , wherein the additives are one or more selected from the group consisting of a dithiophosphate-based abrasion resistant agent, a calcium-based detergent and dispersant, a phosphate ester-based friction modifier, a bis-succinimide-type ashless dispersant, a polysulfide-based extreme pressure agent, and an anti-oxidant. 
     
     
         9 . The gear oil composition of  claim 1 , having an average kinematic viscosity of 7 to 11 cSt at 100° C., an average kinematic viscosity of 30 to 60 cSt at 40° C., and an average absolute viscosity of 10,000 to 50,000 cP at −40° C.