To obtain a composition which shows an excellent friction property and excellent durability and is particularly suitable for a power transmission lubricating oil by mixing a specific amount of a diol compound with a lubricating base oil.
A diol compound represented by the formula is mixed, the amount thereof being 0.01-5.0 mass % of the obtained composition wherein R1 is an 8-30C alkyl or alkenyl and R2 is H or an alkyl or an alkenyl having not more than 8 carbon atoms. Further, a friction controlling agent having no phosphorus, a succinic acid imide-based non-ash dispersing agent, a phosphorus-based compound, a basic metal-based washing agent and/or zinc dithiophosphate, alone or in combination thereof, may be mixed with the composition, the respective amounts based on the total amount of the composition being 0.01-5.0 mass %, 0.5-15.0 mass %, 0.005-0.5 mass % as phosphorus element, 0.1-5.0 mass % and 0.005-5.0 mass %. The base oil to be used includes a mineral oil and a synthetic oil among which an oil having a dynamic viscosity of 1-10 mm2 is preferable.
MURONAKA ISAMU
AOKI TORU
OKAWA TETSUO
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