It is expected that the analysis of the evaporation process for multicomponent fuels such as actual fuels like gasoline and diesel gas oil could be performed to assess more accurately the mixture preparation field inside the cylinder of D.I.S.I engines and diesel engines. In this paper, we suggested the importance of this multicomponent fuel consideration relating to the mixture formation and combustion characteristics from the basis of their own fuel physical and chemical properties. Then, we introduce a treatment for the phase change of a multicomponent solution through the formation of two-phase regions with the basis of chemical-thermodymical liquid-vapor equilibrium. Next, we analyze the distillation properties of a multicomponent fuel as well as the evaporation process of a multicomponent single droplet by use of the chemical-thermodymical analysis. And, we propose a simple estimation scheme for the evaporation process of a multicomponent fuel spray, where the quasi-two phase region is considered. Then, the mixture formation process in the spray was calculated for multicomponent fuel by KIVA-II code. The spray-wall interaction process was also modeled by considering the superheating degree of the surface for the liquid spray droplets based on several experimental results in order to take into account the change in boiling phenomena at the liquid-solid interface during the impingement and post impingement process.