Water and ethylene glycol as conventional coolants have been widely used in an automotive car radiator for many years. These heat transfer fluids offer low thermal conductivity. With the advancement of nanotechnology, the new generation of heat transfer fluids called, “nanofluids” have been developed and researchers found that these fluids offer higher thermal conductivity compared to that of conventional coolants. This study focused on the application of Mixture of water and ethylene glycol based Al2O3 nanofluids in a cooling system. Relevant input data, nanofluid properties and empirical correlations were obtained from literatures to investigate the performance on twin cylinder Diesel engine under different mixtures of nanofluid based coolants and also to investigate heat transfer enhancement of an automotive car radiator operated with nanofluid-based coolants. It was observed that, the performance on Diesel engine and heat transfer rate in engine cooling system increased with the usage of nanofluids (with water and ethylene glycol the basefluid) compared to water and ethylene glycol (i.e. base fluid ) alone.