This study focuses on the aerodynamic performances of two vehicles by Dokuz Eylul University Solaris Solar Car Project Team. The first vehicle (S7) is a solar -powered vehicle that is designed for World Solar Challenge and the second (D9) is an electric vehicle which is designed for Tubitak EV Challenge. Both vehicles are manufactured using polymer composites and challenged in mentioned races. In this research, a formal optimisation technique based on computational fluid dynamics (CFD) is used to determine the efficient aerodynamic structures under various scenarios. Results clearly show that strategists of the racing teams should take into account the aerodynamic structure of the racing car. Especially before the races which based on efficiency, the apex line is determined, and mirrors should be replaced by back view camera.