In this research work, the heat transfer with water based nanofluids was experimentally compared to that of pure water as coolant in an automobile radiator. By varying the amount of Al2O3 nanoparticles blended with base fluid water, two different concentrations of nanofluids 0.25 % and 0.50 % (by vol.) were obtained. These nanofluids were allowed to flow through the vertical tubes present in the radiator. The flow rate ranges from 0.05 to 0.15 kg/s. The fluid inlet temperature was varying from 35°C to 59°C to find the optimum inlet condition. An attempt was also made to maximize the heat transfer rate of an automotive radiator without excessive compromise on radiator pumping loss and coolant cost. Three factors namely nanoparticle concentration, flow rate and inlet temperature of coolant were chosen as the influencing factors for the set objective. Experiments designed by employing design of experiments method and Taguchi’s L9 orthogonal array were adopted to run the automotive radiator test rig. An indigenous automotive radiator test rig was developed as part of this research work. MRSN ratio was calculated for the response variables and the optimum combination level of factors was obtained simultaneously using Taguchi’s parametric design. Obtained combination was confirmed experimentally and significant improvement was observed in the response variables. © 2015, Sphinx Knowledge House. All rights reserved.