Automobile transmission oil composition with improved low-temperature transmission performance

Abstract

The present invention provides a manual transmission oil composition containing a predetermined amount of polyalphaolefin (PAO) synthetic base oil and a predetermined amount of polyalkylmethacrylate having a number-average molecular weight of 300,000 to 400,000 as a viscosity index improver and thus having a high viscosity even at high temperatures and a low viscosity at low temperatures compared to other manual transmission oils having the same viscosity grade (SAE 75W85 grade).

1 . A manual transmission oil composition comprising:
 78 to 80 wt % of polyalphaolefin synthetic base oil;   10 to 12 wt % of polyalkylmethacrylate having a number-average molecular weight of 300,000 to 400,000; and   8 to 12 wt % of at least one additive selected from the group consisting of an anti-wear agent, a metallic detergent-dispersant, a phosphate ester friction modifier, a bis-succinimide ashless dispersant, an extreme pressure additive, and a mixture thereof.   
     
     
         2 . The manual transmission oil composition of  claim 1 , wherein the base oil has an average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 or higher, and a pour point of −60° C. 
     
     
         3 . The manual transmission oil composition of  claim 1 , wherein the polyalkylmethacrylate comprises 60 to 80 wt% of C 12  to C 15  alkyl methacrylate and 20 to 40 wt % of 2-ethyihexyl methacrylate. 
     
     
         4 . The manual transmission oil composition of  claim 1 , wherein the anti-wear agent is zinc dithiophosphate, the metallic detergent-dispersant is calcium sulfonate, and the extreme pressure additive is polysulfide. 
     
     
         5 . A manual transmission oil composition comprising:
 78 to 80 wt % of a synthetic base oil;   10 to 12 wt % of a viscosity index improver; and   8 to 12 wt % of at least one additive selected from the group consisting of anti-wear agents, metallic detergent-dispersants, phosphate ester friction modifiers, bis-succinimide ashless dispersants, extreme pressure additives, and a mixture thereof.   
     
     
         6 . The manual transmission oil of  claim 5 , wherein the synthetic base oil has an average kinematic viscosity ranging from about 3 to 8 cSt at 100° C. 
     
     
         7 . The manual transmission oil composition of  claim 5 , wherein the viscosity index improver has a number-average molecular weight of 300,000 to 400,000. 
     
     
         8 . A manual transmission oil composition comprising:
 78 to 80 wt % polyalphaolefin synthetic base oil;   10 to 12 wt % of a viscosity index improver having a number-average molecular weight of 300,000 to 400,000; and   one or more additives selected from the group consisting of anti-wear agents, metallic detergent-dispersants, phosphate ester friction modifiers, bis-succinimide ashless dispersants, and extreme pressure additives.