An autoignition DI methanol engine has been developed to improve the thermal efficiency under low load conditions. The engine was compared with glow-assisted and spark-assisted DI methanol engines, and with conventional DI diesel engines.The results show that the autoignition occurs when the gas temperature in the cylinder exceeds approximately 900K. In the autoignition DI methanol engine, combustion proceeds rapidly, which results in high peak of heat release and short combustion duration. The thermal efficiency of the autoignition DI methanol engine, therefore, is higher than that of other type methanol engines and almost the same as that of diesel engines under low load conditions. NOx of the autoignition DI methanol engine is the lowest since it has the highest EGR.