A weighted mean activation energy method was applied to describe the reactivity and combustibility of crude oils via simultaneous TG/DTG. Thermal experiments were conducted with a non-isothermal method at a heating rate of 10‡C min−1 with excess air. Reaction rates increased progressively with increasing temperature. The rate data were fitted to an Arrhenius equation; the plots showed three distinct reaction regions. Weighted mean activation energies (Ewm), of the crude oils were calculated and a correlation was established betweenEwm, API gravity and peak temperatures during high-temperature oxidation.