Maleic anhydride was added (2%) to rapeseed oils before their oxidn. at 150 degrees C for 70 or 100 min to improve the stability of the oils. The oils were studied for fractional compn., kinematic viscosity, acid no. and peroxide value directly after the oxidn. and after 1 year long storage in air. The addn. of maleic anhydride resulted in a shortening of oxidn. time, increasing the oxidative stability of the oils and improving their lubricating capacity.