Mine gases, in which the power factor is given by methane, have different chemical compositions and physical properties. These gases can be fuels for internal combustion engines. The diversity of gas parameters combined with downsizing, which is a trend in the development of internal combustion engines, is the foundation of this project, for which the research problem has been defined as an assessment of the impact of lowmethane fuel on engine operating indicators. It has been shown to be possible to use a methane-downsized engine instead of gasoline by the application of high-energy fuel with methane content higher than 60%. The results have been obtained by modeling engine cycles, hence the next step in research will be testing on real objects.