The main target of this project is to make an aerodynamic study of the rear spoiler of a Formula World Series by Renault 3.5. Its behaviour is shown under the influence of different variables such as fluid velocity, angle of attack of the spoiler, turbulence, viscous model or mesh size, Each one of the previous factors was chosen carefully in order to achieve the more realistic result. Firstly, the spoiler airfoil was analyzed in 2 dimensions, to get a rough idea of the influence of the different variables and its behaviour. Once these values were obtained, a 3 dimensional analysis was done. In this three dimensional analysis only one half of the spoiler was considered, taking advantage of its symmetry with respect its central plane. This allows to reduce the computing time, without losing reliability. Finally, the results obtained in 2 and 3 dimensions are presented, compared and discussed.