Lubricating oil composition for continuously variable transmission

Abstract

A lubricating oil composition for a continuously variable transmission has low viscosity to exhibit fuel savings, higher metal-to-metal friction coefficient to ensure high power transmission, wet clutch friction characteristics and anti-shudder properties required for transmissions, and low traction coefficient to achieve fuel savings. The composition contains a base oil adjusted so the product (EC×V40) of the mass % (ECmass %) of saturated cyclic component based on the total base oil and the 40° C. kinematic viscosity (V40 mm 2 /s) is 500 or less and the 100° C. kinematic viscosity is 3.6 to 4.1 mm 2 /s, (B) a phosphorus compound, (C) a calcium salicylate and/or a calcium sulfonate, (D) a boron-modified ashless dispersant in an amount of 0.001 to 0.008 mass % as boron, and (E) a friction modifier, each in a specific amount, the lubricating oil composition having a 100° C. kinematic viscosity of 5.2 to 5.6 mm 2 /s and a viscosity index of 165 or greater.

1 . A lubricating oil composition for a continuously variable transmission, comprising a base oil having been adjusted so that the product (EC×V40) of the mass percent (EC (mass %)) of a saturated cyclic component on the total base oil mass basis and the 40° C. kinematic viscosity (V40 (mm 2 /s)) is 500 or less and the 100° C. kinematic viscosity is from 3.6 to 4.1 mm 2 /s, (B) a phosphorus compound in an amount of 0.01 to 0.03 percent by mass as phosphorus, (C) a calcium salicylate and/or a calcium sulfonate in an amount of 0.03 to 0.05 percent by mass as calcium, the elemental ratio (P/Ca) of phosphorus and calcium in the lubricating oil composition being from 0.3 to 0.7, (D) a boron-modified ashless dispersant in an amount of 0.001 to 0.008 percent by mass as boron, and (E) a friction modifier in an amount of 0.01 to 2 percent by mass on the total composition mass basis, the lubricating oil composition having a 100° C. kinematic viscosity of 5.2 to 5.6 mm 2 /s and a viscosity index of 165 or greater. 
     
     
         2 . The lubricating oil composition for a continuously variable transmission according to  claim 1  wherein Component (E) is a fatty acid ester-based friction modifier and/or a fatty acid amide-based friction modifier.