Abstract: For the purpose of mitigating motor cars to rely on petroleum and to reduce the air pollution in our country， the experimental studies on the mixed fuel of petroleum with high methanol content （M 85） were carried out in the EQ 6100 car engines which are of a great number available and extensively used in China． The experiment results showed that after the structure refitment and the regulation of design parameter of the engine for the new mixed fuel， the performance of power, economy and ejected exhaust gas were improved or raised by a big margin. The methanol fuel thus can be fully put into operation on the existing refitted gasoline engines. 