The power developed by the engine of the automobile is used to overcome the drag. This lost power affects the mileage. Aerodynamic drag also creates noise. Therefore, aerodynamic drag is not desirable.
The aerodynamic drag increases with the speed of the vehicle. Automobiles are designed to overcome drag and air resistance. This is done by making the vehicle streamlined with a smooth surface, avoiding sharp edges. In many vehicles, the lights and the wheel arcs are designed as part of the vehicle.