Cooling is one of the most important challenges facing engines performance. Due to limited space at the front of the engine, the size of the radiator is restricted and cannot be essentially increased. Therefore, it is necessary to increase the heat transfer capabilities of working fluids. With the advancement of nanotechnology, the new generation of heat transfer fluids called, nanofluids have been developed and these fluids offer higher heat transfer properties compared to that of conventional automotive engine coolants. Nanofluids seem to be potential replacement of conventional coolants in engine cooling system. Recently there have been considerable research findings highlighting superior heat transfer performances of nanofluids about 15-40% of heat transfer enhancement can be achieved by using various types of nanofluids. With these superior characteristics, the size and weight of an automotive car radiator can be reduced without affecting its heat transfer performance.