The invention relates to a method for operating at least one precombustion chamber-fired internal combustion engine, in particular a stationary gas Otto cycle engine, having a pilot chamber and a main combustion chamber associated with the precombustion chamber, wherein a gas mixture is fed to the precombustion chamber as flushing gas, wherein a synthesis gas generated in a fuel reformer and a fuel from a fuel source are fed to the flushing gas and wherein a fuel and at least one further substance stream are fed to the fuel reformer for the reforming process, wherein at least one operating parameter of the at least one internal combustion engine is monitored, wherein in accordance with a change in the at least one operating parameter the chemical composition of the flushing gas is modified by changing the mass stream of the at least one further substance stream.