The ignition delay times of lean (? = 0.5) propane/oxygen/argon mixtures were measured in the temperature range 750 K ? T ? 1300 K at pressures of 10 and 30 bar, respectively. The comparison with experiments in air [1,2] show that there is a good agreement at temperatures < 1050 K whereas at lower temperatures the ignition delay times of the present experiments are up to a factor of two shorter. This study confirms that the activation energy of the ignition delay time decreases at around 1050 K and a linear extrapolation is not possible. Reaction schemes used in literature cannot predict the ignition delay times at these low temperatures. ICCD pictures taken shortly after the ignition through the transparent end flange show that the ignition occurs in the middle of the shock tube.