The purpose of this research is to explore the world of Computer-Aided Modelling and then apply its tools to benefit the automotive sector. Three commercially available economical vehicles in Pakistan, namely (i) Daihatsu Mira X, (ii) Honda N-One and (iii) Suzuki Wagon R, have been virtually modelled in Computer-Aided Design (CAD) software by using CATIA-V5R19. This research focuses on providing all the steps that are needed to transform an existing real vehicle body to a virtual vehicle body. Detailed comparisons of all the three hatchback vehicles have performed which determined the most crucial factors of the body that affect the performance of the vehicle. Computational fluid dynamics (CFD) analysis is also performed using SolidWorks flow simulation tool. The base drag and lift coefficients of selected vehicles are computed and compared. Furthermore, the influence of different diffuser angles on the aerodynamics characteristics of vehicle is also investigated. The drag and lift coefficients are computed at different diffuser angles to find out the optimum angle of diffuser. With the increase in diffuser angle, it is found that the total lift coefficient decreases but there is not much effect on drag coefficient for all hatchback vehicles. In addition, this study revealed that Daihatsu Mira X is the most stable and fuel economic vehicle among all three considered vehicles because of its lower centre of gravity co-ordinates and smaller coefficient of drag values at all diffuser angles.