Liquefaction of polypropylene, polyethylene and polystyrene by oxidative degradation with gas oil as a carrier and phenol as a catalyst was performed in an autoclave. Air pressure, temperature and reaction time were varied. The advantage of this process is the production of non-oxygenated lighter compounds, mainly saturated hydrocarbons, from the polyolefins. The optimum cracking conditions were 0.7 MPa air pressure, 400 degrees C and 30 min reaction, yielding 32 wt% gasoline, 15 wt% kerosene and 27 wt% gas oil from the degraded oil of polypropylene. These products had petroleum-like properties according to ASTM and IP test methods. Furthermore the oils obtained can be used as chemical feedstocks. From the results, a reaction mechanism is proposed which postulates (1) thermal elimination of hydrogen atoms from hydrocarbon molecules via interaction between phenol and oxygen molecules (initial step), (2) degradation of the resulting hydrocarbon macroradicals through p-scission, producing relatively low-molecular-weight end-chain radicals and (3) free radical transfer reactions via phenoxy radicals, with steps (2) and (3) producing competitive acceleration of the hydrocarbon degradation in a random scission mechanism.