In this study, 16 experiments were conducted to study the effects of pressure on crude oil oxidation in limestone medium. Karakus (29 degrees API), Beykan (32 degrees API), Bati Raman (12 degrees API), Camurlu ( 12 degrees API), Adiyaman (26 degrees API), Garzan (28 degrees API) and Raman (18 degrees API) crude oil from Turkish oil fields were used. The mixture of limestone and the crude oil was subjected to a controlled heating schedule under a constant flow rate of air. The produced gas was analyzed for its oxygen and carbon oxides contents. The results of reaction kinetics showed that the molar CO2/CO ratio values of fuel combustion increased with increasing pressure. A decrease in the atomic H/C ratio with an increase in temperature was observed for all runs. Results indicate that oxygen consumed increases with increasing operating pressure. This means more fuel is burnt by increasing the pressure, which is due to the effect of pressure on the volatility of the oil components. Because increasing pressure will depress oil volatility, the fuel availability would increase. This also suggests that distillation might be the dominant mechanism for fuel deposition. A trend of increase in activation energy values by increasing pressure is observed.