Abstract: A method of operating an internal combustion engine with alternative preheated fuels, or mixtures thereof, at the same compression ratio and supplied with an additional medium for the operation comprisesdetecting the flow of air drawn into the engine through the air intake,proportioning and distributing the fuel to each cylinder in response to at least detected flow,heating the fuel fed to each cylinder to a temperature between its flame temperature and above its evaporation temperature, but below its auto ignition temperature, andinjecting the heated fuel and the additional medium in a controlled amount into each cylinder through separate feed means at different angles with respect to the wall of the respective cylinder.