A method and apparatus for the mixture preparation of internal combustion engines in which an adaptation of the suction air temperature to the varying operating and load conditions of internal combustion engines for motor vehicles is achieved; possibly exclusively preheated air is thereby supplied to the internal combustion engine by way of the suction system in the partial load range while exclusively fresh air flows into the combustion engine in the full load range whereby the warm air serving for the mixture formation has a substantially constant temperature over the entire range of its admixture.