In this research, the effect of inlet pressure on combustion behavior of medium and light crude oils was analyzed with TGA and DSC experiments. The ramped temperature combustion experiments were performed at constant heating rates under air atmosphere. TGA curves revealed three main reaction regions known as low temperature oxidation (LTO), fuel deposition (FD), and high temperature oxidation (HTO). In DSC curves, at the early stage of the heating, distillation region was also observed in addition to LTO and HTO reaction regions. It was observed that the changes in inlet pressure affect the temperature intervals of the reaction regions and peak temperatures. The kinetic parameters were calculated according to Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS), and ASTM methods. Results indicated that the increase in inlet pressure increased in the activation energy.