Blendings of methanol and diesel fuel can only be produced in form of emulsions. The stability of those emulsions strongly depends on the concentration of surface active agents. It is shown that observed changes in mixture formation of emulsions in comparison to pure diesel fuel conditions can be explained by a theory of spontaneous evaporation. Several feasible droplet models are discussed. Emulsion droplets evaporate spontaneously if the droplet temperature exceeds the superheating limit of the disperse phase. The superheating limit is only exceeded at the outer zone of the injection jet.