A control unit and a method for checking the outgassing of fuel from the lubricant of an internal combustion engine are provided, wherein, in a first method step, the outgassing of fuel from the lubricant is estimated on the basis of at least one operating parameter using a theoretical model during the normal operation of the internal combustion engine, and wherein, after the estimation of defined outgassing of fuel on the basis of the model, the outgassing of fuel is estimated in a second method step on the basis of at least one further operating parameter during a defined operating state.