A corn. mixt. of palm, rapeseed and sunflower oils used for frying was analyzed for chem. compn. by gas chromatog. and detn. of I, acid, epoxide, hydroxy, peroxide and anisidine nos. before and after use and then epoxidized with H2O2/AcON mixt. at 25-70 degrees C. The epoxidized oils were also characterized with I, epoxide, acid and hydroxyl nos. as well as by H-1 NMR and C-13 NMR spectroscopies. The spent oil after epoxidation met the requirements for oligoesterols for prodn. of polyurethane foams.