PURPOSE: To provide an automatic transmission oil composition which is excellent in friction characteristics, nonfoamability, etc., and does not leak from breathers by incorporating a dimethylpolysiloxane specified in viscosity and a specific friction controlling agent in a base oil in respectively given amounts.
CONSTITUTION: The title composition comprises a base oil, 0.01-5wt.% compound(s) selected from the group consisting of phosphoric (phosphorous) esters or amine salts, 8-30C aliphatic or aromatic carboxylic acids, reaction products with esters or organic amines of the above acids, hydrocarbon sulfides (e.g. diisobutyl disulfide) represented by the formula (wherein R1 is a monovalent hydrocarbon group; R2 is a divalent hydrocarbon group; X is an integer of 1 or more; (n) or 0 or 1 or more), and sulfurized fat or oil which is a reaction product of a fat or oil with sulfur, and 0.00003-0.005wt.% dimethylpolysiloxane having a viscosity at 25°C of 50 to 500 thousand cSt.
TOCHIGI HIROSHI
ISHIHARA MASATOSHI
COSMO OIL CO LTD