PURPOSE: An oil composition for refrigerator that contains, as the major component, a specific bicyclic compound with a specific dynamic viscosity, thus showing good wearing resistance and high stability to coolant and reducing the consumption of electric power.

CONSTITUTION: The objective composition is composed of (A) a bicyclic compound which is shown as the formula (R1, R2 are 1W5C alkyl; R3 is H, 1W5C alkyl; m, n are 0W5) and has a dynamic viscosity of 5W20cst at 40°C, as the major component, and preferably further (B) 1ppmW10wt% at least one of additives selected from the group consisting of acid acceptors, abrasives, antioxidants and defoaming agents. The component A is prepared by alkylation reaction between an aromatic vinyl compound such as styrene or α-methylstyrene and an alkyl aromatic compound such as toluene or xylene.