The main objective of the study is to reduce the aerodynamic drag and increase the stability of the car on the road for a three dimensional full-sized Super Utility Vehicle (SUV) using Computational Fluid Dynamics (CFD). The study calculates the pressure and the streamline of velocity around the car. The SUV baseline model in the simulation is Mercedes - Benz GL class model 2013. Modifications and aerodynamic add-on devices are used to improve the aerodynamic behaviour of the Mercedes - Benz GL class model 2013. There are many modern aerodynamic add-on devices which are used in this research, such as many types of the spoiler, ventilation duct, mud flaps, vortex generators, ditch on the roof and diffuser. New design of devices is used to improve the aerodynamic performance of the SUV model. All of these tools are used individually or in combination. The improvement of aerodynamics should not mainly affect the vehicles capacity and comfort. This study has dealt with three boundary conditions for the velocity of the air, one with airflow of 28 m/s (100.8 km/h), 34 m/s (122.4 km/h) and 40 m/s (144 km/h). At 28 m/s an aerodynamic drag reduction of up to 25.64% compared with the baseline is achieved for Mercedes Benz GL class, model 2013 with all modifications and add-on devices. It is clear that the use of ventilation duct has a significant effect in reducing aerodynamic drag. A steady increase in global energy demand has a direct inﬂuence onthe fuel prices.