Abstract: A method for operating a reciprocating-piston internal combustion engine, including: supplying a fuel mixture having two fuel types and air into a combustion chamber; burning the fuel mixture in the combustion chamber during a working stroke; detecting the pressure profile in the combustion chamber during the working stroke by one pressure sensor per combustion chamber; determining an amount of energy per working stroke and per combustion chamber from the pressure profile. In order to enable different fuel types and/or fuel qualities to be taken into consideration in the regulation of the engine, the calorific value of the fuel mixture per working stroke and per combustion chamber is determined from the volume and/or the mass of the supplied fuel mixture and from the determined amount of energy per working stroke and per combustion chamber. At least one parameter of the engine is regulated as a function of the calorific value.