Rapeseed oil was thermally polymerized in presence of maleic anhydride (1) and O(g) at 150 degrees C to a lubricating oil. The oil was studied by thermal anal. for oxidn. resistance and freezing point as well as by tribolog. tests for lubricating and antiwear properties. Chem. compn. of the oil was detd. by gel permeation chromatog. The thermal polymn. without I resulted in a decrease in the oxidn. resistance of the oil. The addn. of I polymn. resulted to the crude rapeseed oil before in an increase in the seizure resistance of the lubricated systems.