A novel supercritical-pressure jet stirred reactor (SP-JSR) was developed to study fuel chemistry at low and intermediate temperatures at extreme pressures up to 200 atm. Propane oxidation at pressures of 10 and 100 atm and over a temperature range of 500-900 K were studied with and without CO2 additions by using the SP-JSR. The experiment showed that at 100 atm, a weak NTC behavior is observed and the intermediate temperature oxidation is shifted to lower temperatures. Furthermore, the results showed that CO2 addition at supercritical conditions has little effect on the low temperature oxidation. The Aramco model under-predicted the NTC behavior and showed little sensitivity of the effect of CO2 addition on the propane oxidation.