PURPOSE: An automatic transmission fluid composition is provided to improve the fuel efficiency by improving low temperature fluidity with low viscosity in low temperature while having good durability required for an automatic transmission with high viscosity in high temperature.;CONSTITUTION: A low temperature low viscosity automatic transmission fluid composition includes lubricant base oil with 55- 65 weight% having saturated hydrocarbon content of 90% or greater and sulfur content of 0.03% or less with100°C kinematic viscosity of 3.0-3.5 cSt, lubricant base oil with 18- 23 weight% with100°C kinematic viscosity of 4.0-4.5 cSt, viscosity index improver with 2- 12 weight% and additive with 10- 20 weight%. The lubricant base oil with100°C kinematic viscosity of 3.0-3.5 cSt features the viscosity index more than 110, the pour point less than -20°C and the lubricant base oil with100°C kinematic viscosity of 4.0-4.5 cSt features the viscosity index more than 120, the pour point less than -10°C. The viscosity index improver has the number average molecular weight ranges from 80000 to 250000. The viscosity index improver is a polyalkyl methacrylate. The polyalkyl methacrylate includes an alkyl methacrylate with 60-80 weight% of C12-C15 and 2-ethylhexyl methacrylate with 20-40 weight%. The 100°C kinematic viscosity of the polyalkyl methacrylate is more than 1500 cSt. The additive includes a mixture of more than one or two of an ashless dispersant, an antioxidant, a phosphate anti-wear agent or a friction modifier. The ashless dispersant is manufactured by reacting succinic polyamine substituted with polyisovuetenyl with a molecular weight of 80-120.;COPYRIGHT KIPO 2013
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