Imperial Oil Co., Toronto, is beginning an asset allocation study of its C$2 billion (U.S. $1.5 billion) pension fund, said Ken Bowman, manager of pension and employee funds. Mr. Bowman said it is likely changes would be made within the next year but would not give specifics. No date has been set for completion of the study. The fund's current asset mix is 30% Canadian stock, 30% international equity and 40% Canadian bonds.