A new method for the use of methanol in IC engine was proposed. Methanol was evaporated into vapor by IC engine exhaust heat and used as gas fuel. This concept was applied to both naturally aspirated engine and turbocharged engine. By comparing the two schemes with the original gasoline engine, the improvement potentials of power performances and fuel economy of new concepts can be predicted.The results have shown that, when naturally aspirated engine is fueled with methanol vapor, power has a slight decline with the maximum of 7.1%, and thermal efficiency has a slight increase with the maximum of 3.0 percentage points; when turbocharged engine is fueled with methanol vapor, the power performance and fuel economy have a great improvement over both the original gasoline engine and methanol vapor engine. At the boost pressure of 1.5 bar, the maximum improvement of thermal efficiency comes up to 4.0 percentage points. All these can prove that it is a useful concept for IC engine energy conservation.