Vehicle auxiliary heater with detection of the fuel quality

The auxiliary heating device (16) has a fuel supply (22) for supplying fuel to a burner (20) of the auxiliary heating device (16) and a control device (28) for controlling the operation of the auxiliary heating device (16). In order to further reduce the pollutant emissions and fuel consumption of the auxiliary heating device (16) in particular, the control device (28) is configured to receive a signal by means of which a statement about the quality of the supplied fuel is possible, and to control the operation of the auxiliary heating device (16) as a function of this signal.