Recently, the issue of energy efficiency is one of the most studied topics. This issue is ever-increasing investigated in automotive sector. In this context, improving thermal performance and heat transfer effectiveness of an automobile radiator which are the most important components of the automobile cooling system, are very important subject of study. Automobile radiator that is a compact cross-flow water to air heat exchangers. In this study, while the length and width of the radiator kept constant, the effect of number of tubes, diameter of tubes, velocity of air, number of fins and the material of fins into the radiators thermal performance and effectiveness were numerically investigated using ANSYS Fluent. In conclusion; with increasing the air velocity, the number of the tubes, diameter of the tube and the number of the fins, it is observed that radiators effectiveness was increased, consequently thermal performance was increased. Additionally, it is also observed that, instead of aluminium, using copper as a material of fin is a better option for thermal performance.