The aerodynamic performance of passenger cars is focused on this research work for reduction of aerodynamic drag force. Better aerodynamic car design will reduce the aerodynamic drag force which will save more fuel, good stability and handling on vehicle. Aerodynamic drag force on the car occurs due to the car profile design and its surface while moving with high speeds. When the car accelerates above 70 kmph, energy available on the flow is less due to the flow separation at rear side of the vehicle. Hence, flow is hesitated to move past the sharp corner on the rear side. This flow separation will produce significant wake on rear side of the car and increase the aerodynamic drag force. This paper proposes a method to reduce the wake region at rear side of the vehicle and to enhance the aerodynamic performance of vehicle by add-on device like vortex generator (VG) attachment on the vehicle. The computational studies have been carried out to study the effect of VG attachment on the vehicle for reduction of aerodynamic drag force. The computational studies are done with real road flow conditions for sedan car model with and without attachment of VG. Result of each car model has been compared with contour of pressure distribution, velocity flow field and turbulent kinetic energy. From computational simulation studies, it has been observed that aerodynamic drag coefficients of car model without VG attachment is 0.3371 and after implementing the VG with optimized parameter in the car has been reduced to 0.3161 at velocity 20 m/s. It has been observed that percentage of reduction of coefficient of drag is 6.22%.