The temperature dependence of the thermal oxidation of sintered silicon carbide (SiC) used for diesel particulate filter walls (DPF) is investigated. Silicon carbide samples are heated at temperatures between 770 K and 1470 K for different annealing times to study the effect of both the temperature and the duration on the oxidation kinetics. The thickness and composition of the oxide layers are characterized by means of XPS and RBS. Silicon oxycarbides (SiCxOy) are first formed and then silicon dioxide (SiO2) appears above 770 K. Different types of SiO2 layers can be identified. The compounds obtained depend on thermal oxidation conditions.