With an increasing CR, the CGP increased generally with the usage of pure ethanol and methanol as compared to unleaded gasoline study and rose earlier than those in unleaded gasoline fuel. When all three fuels were compared for the maximum CGP values, they were demonstrated to be about 4502.37 kPa at a CR of 9.0:1 with gasoline, 4747.05 kPa at a CR of 9.5:1 with ethanol, and 4994.1 kPa at a CR of 9.0:1 with methanol. According to the obtained results of gasoline fuel at the original CR, the maximum values of the CGP of pure ethanol and methanol increased to about 51.57% and 59.46%. They had lower values and earlier constitutions of HRR in ethanol and methanol than that of gasoline fuel.