An engine cooling system in a vehicle engine is a must, which carries away unutilized heat produced in the engine cylinder. However, usage of low thermal conductivity engine coolant limits the ability of the cooling system to extract the heat, which ultimately results in difficulties in maintaining the compact size of the cooling system. Also, increasing the cooling rate by conventional technologies i.e. providing fins and microchannel has already reached their limits. Researchers are thus focusing on immersing and analyzing new types of cooling fluids in recent days. In the present study, the thermal performance of two different nanofluids, Al2O3 and CuO in a flat tube automobile radiator has been studied. Experimental results have been obtained for 0.02% volume concentration of both Al2O3 and CuO nanofluid, and water as coolants. A numerical model considering the ε-NTU method is also developed using MATLAB code. The analytical results are validated with experimental results. Further, the validated model is applied to study the variations of heat transfer rate, heat transfer coefficient with Reynolds number and source temperature for all the different coolants. Clearly, both of the nanofluids are superior to water. The heat transfer rate and heat transfer coefficient show increment with an increase in volume concentration. Further, it is concluded that among the two, Al2O3 nanofluid performed better than CuO, owing to its better heat transfer rates.