The article describes the technical characteristics for two gasoline engines that are converted to methane fuel. The study was carried out on the basis of mathematical modeling in the Diesel-RК program. It is shown that the conversion of gasoline engines to methane leads to a power reduction in the range of 7.5% with a decrease in specific fuel consumption to 12%, as well as a reduction in NOx emissions by 2-3 times. It is revealed that an increase in the compression ratio to 15 leads to an increase in the power and environmental friendliness of the gas piston engine.