The thermal-oxidative stability of unleaded motor gasolines of diverse composition and origin were measured using pressure differential scanning calorimetry (ps.c.) in the temperature programmed mode. The samples were exposed to a heating profile of 1 degrees C min(-1) under 2000 kPa oxygen pressure from 80 degrees C to 200 degrees C. From the resulting d.s.c. exotherms, the oxidative induction temperature was determined and used for the assessment of thermal-oxidative stability. For the seven gasolines investigated, the ranking obtained from this test method was consistent with that of the norm method ISO 7536, when taking into account the amount of potential gum formed during the aging time of 960 min. Moreover, the experiments gave recognizably different thermograms as well as onset temperatures for each gasoline, so proving that dynamic ps.c. is a useful tool for evaluating the oxidation characteristic of low-boiling hydrocarbon mixtures. The results confirmed the fact that the larger the amount of olefinic and diolefinic compounds, the more susceptible gasolines are to oxidation, showing under the ps.c. operating conditions an increasing gum-forming tendency.