The invention relates to the supply of lamps of at least two different lamp types, of which a first lamp type has a wattage which is approximately a whole multiple of the wattage of a second lamp type, whereby the same ballast devices are used, embodied for the direct supply of the second lamp type and which may be operated in parallel for the supply of the first lamp type. The ECU adjusts each of fuel injection amounts to suppress engine revolution speed change and engine vibration caused by differences of combustion power between cylinders. The mixer is connected to the nozzles for feeding them with the mixture.