Abstract: A device for operating an internal combustion engine with a fuel. The device determines a standard ignition angle for an actual operating point of the internal combustion engine on the basis of ignition angle characteristic data, and determines a knock limit distance of the standard ignition angle from a knock limit of the internal combustion engine on the basis of knock limit distance characteristic data for the actual operating point of the internal combustion engine. The device also determines an operating ignition angle for the operation of the combustion engine and/or an actual RON value of the fuel on the basis of the standard ignition angle and on the basis of the knock limit distance.