Reducing vehicle fuel consumption has become one of the most critical issues in recent years. The main objective of this paper is to investigate how wind deflectors impact aerodynamic characteristics in a simplified box truck model. Three wind deflector model variants were studied. The computational fluid dynamics (CFD) software and steady Reynolds-Averaged Navier-Stokes (RANS) equations with the Realizable k-ε model were used to simulate at a velocity of 30 m/s. The deflector shape’s effect on a truck model’s aerodynamic performance, such as drag coefficient, pressure and velocity was investigated. The results indicate that the use of a wind deflector can reduce the drag coefficient by 24.3% compared to a truck without a wind deflector, leading to decreased fuel consumption.