Aerodynamic characteristics of passenger cars have been a fruitful area of research for several years, and continue to this day. The Ahmed body represents simplified geometry of generic passenger car that can be used to study the flow characteristic of vehicles. The main objective of this paper is to understand the aerodynamic characteristics and drag reduction techniques of an isolated passenger car. To study this problem, Ahmed car model with different rear slant angles (0°- 40°), is simulated at the air velocity of 35 m/s using CFD. Also the effect of Reynolds Number, Ground clearance and rear end drag reduction techniques (varying fore body rounding and boat-tailing) on drag coefficient is identified. The computational part includes numerical simulation of the flow around the Ahmed car body employing CFD (Computational Fluid Dynamics) techniques. The designing of model and CFD simulation is carried out in FLUENT (ANSYS 15.0). Major findings show that the rear part of the vehicle plays a major role in formation of wake. Significant drag reduction was observed for 25° rear slant angle resulting from the reduced recirculation region behind the model.