Recently Pre-Ignition in Premixed Combustion Engines are reported in many studies. Pre-Ignition is assumed to be caused by lubricant oil (LO). But, LO auto-ignition condition and the potential of LO auto-ignition on Pre-Mixture ignition has not been clarified. Therefore, this study focuses on the auto-ignition of LO and the ignition of Pre-Mixture induced by auto-ignition of LO. The experiment was conducted by Rapid Compression Expansion Machine (RCEM) to simulate engine operating condition. From experimental result, LO is able to ignite Pre-Mixture gas under engine operating conditions. Pre-Ignition (ignition of Pre-Mixture by auto-ignition of LO) can be inhibited by decreasing equivalence ratio and temperature of Pre-Mixture or increasing engine speed.