Lubricating oil composition for automatic transmission
This invention provides a lubricating oil composition for automobile transmission that includes: as low-viscosity base oils: (i) between 45 and 95 mass % of a Fischer-Tropsch synthetic low-viscosity base oil with a 100° C. kinematic viscosity of between 1 mm 2 /s and 2 mm 2 /s, and between 0 and 25 mass % of other than a Fischer-Tropsch synthetic low-viscosity base oil with a 100° C. kinematic viscosity of between 1 mm 2 /s and 2 mm 2 /s, and (ii) between 0 and 35 mass % of a base oil wherein the 100° C. kinematic viscosity is greater that 2 mm 2 /s and no greater than 5 mm 2 /s; and (iii) between 5 and 55 mass % of an olefin polymer or copolymer, as a high-viscosity base oil, wherein the 100° C. kinematic viscosity is between 100 and 800 mm 2 /s. A lubricating oil composition for an automatic transmission wherein the 100° C. kinematic viscosity of this composition is between 3.8 and 5.5 mm 2 /s, the viscosity index is no less than 190, the flashpoint is no less than 140° C., and the reduction ratio of the 100° C. kinematic viscosity after shear stability testing, at 60° C. for 20 hours, is maintained at no greater than 3%.
1. A lubricating oil composition for an automatic transmission, the lubricating oil composition comprising
(a) a first low viscosity oil base oil at a concentration of between 45% and 95% by mass,
wherein the low viscosity base oil comprises a Fischer-Tropsch synthetic low-viscosity base oil, and
wherein the low viscosity base oil has a kinematic viscosity of between 1 mm 2 /s and 2 mm 2 /s at 100° C.,
(b) a second low viscosity base oil at a concentration of between 0% and 25% by mass,
wherein the second low viscosity base oil is not a Fischer-Tropsch synthetic low-viscosity base oil, and
wherein the second low viscosity base oil has a kinematic viscosity of between 1 mm 2 /s and 2 mm 2 /s at 100° C.,
(c) a base oil at a concentration of between 0% and 35% by mass,
wherein the base oil has a kinematic viscosity of between 2 mm 2 /s and 5 mm 2 /s at 100° C., and
(d) a high viscosity base oil at a concentration of between 5% and 55% by mass,
wherein the high viscosity base oil comprises one of an olefin polymer and a co-polymer, and
wherein the high viscosity base oil has a kinematic viscosity of between 100 mm 2 /s and 800 mm 2 /s at 100° C.,
wherein the lubricating oil composition has:
a kinematic viscosity of between 3.8 mm 2 /s and 5.5 mm 2 /s;
a viscosity index is no less than 190;
a flashpoint of equal to or greater than 140° C., and
a rate of reduction in a 100° C. kinematic viscosity of not more than 3%, as measured after a KRL shear stability test having been performed at 60° C. for 20 hours.
2. The lubricating oil composition according to claim 1 , wherein the high-viscosity base oil has a 100° C. kinematic viscosity of between 200 mm 2 /s and 700 mm 2 /s.
3. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition a kinematic viscosity of between 4.5 mm 2 /s and 5.2 mm 2 /s.
4. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition has a flashpoint equal to or greater than 160° C.
5. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition has a 0° C. kinematic viscosity of less than or equal to 120 mm 2 /s.
6. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition has a Noack evaporation loss of not more than 50 wt %.
7. The lubricating oil composition according to claim 1 , wherein the low viscosity base oil has a kinematic viscosity of between 1.2 mm 2 /s and 1.8 mm 2 /s at 100° C.
8. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition further comprises one or more of an extreme pressure agent, a dispersing agent, a metal-based cleaning agent, a friction adjusting agent, an oxidation inhibitor, a corrosion inhibitor, a rust inhibitor, an anti-emulsifying agent, a metal deactivating agent, a pour point depressing agent, a seal swelling agent, an anti-foaming agent, and a coloring agent.
9. The lubricating oil composition according to claim 1 , wherein the lubricating oil composition has the rate of reduction in the 100° C. kinematic viscosity of not more than 1%, as measured after the KRL shear stability test having been performed at 60° C. for 20 hours.
10. The lubricating oil composition according to claim 1 , wherein the co-polymer is an ethylene-alpha olefin copolymer.
11. The lubricating oil composition according to claim 1 , wherein the base oil comprises one of a group 2 base oil, a group 3 base oil, and a group 4 base oil, as classified by the American Petroleum Institute base oil classifications.
12. The lubricating oil composition according to claim 1 , wherein the sulfur content of each of the first low viscosity base oil and the second low viscosity base oil is less than 1 ppm.