Lubricating oil compositions for automatic transmissions

Abstract

A lubricating oil composition for automatic transmissions wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), the concentration of phosphorus is from 0.01 to 0.06 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition. The lubricating oil composition can prevent the occurrence of scratch phenomenon even over a long period of time when used in a metal belt type continuously variable automatic transmission.

1 . A lubricating oil composition for automatic transmissions wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), the concentration of phosphorus is from 0.01 to 0.06 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition and.  
     
     
         2 . The lubricating oil composition according to  claim 1  wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 1):(0.1 to 0.8):(0.4 to 5), the concentration of phosphorus is from 0.02 to 0.05 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition.  
     
     
         3 . The lubricating oil composition according to  claim 1  or  2  wherein said sulfur-based additive is at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E).