Computational Fluid Dynamics is used to assess the thermal (heat transfer) performances of an automobile engine considering different grille opening and closing degrees. For this purpose the entire vehicle is modelled and three fundamental aspects are examined, namely, the open area of the air intake grille, the position of the upper and lower grilles and their shape. The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile. With an increase in the opening angle of the grille, the C D (Drag Coefficient) value of the whole vehicle becomes higher. When the air intake grille of the car is fully open or closed, the C D value is 0.35434 or 0.31777, respectively, that is, the flow resistance in the engine compartment accounts for 10.32% of the C D value for the whole automobile.