Consumption of natural resources is aggravating at an astonishing rate and soon this will lead to scarcity for future generations. The engineering fraternity is constantly engaged in identifying innovative solutions to save energy and reduce consumption. Acknowledging this, one of the innovative ways of increasing heat transfer rates in engine cooling systems has been targeted. The theory says, the hydraulic diameter of tubes plays a vital role in tube-fin heat exchangers, reducing the diameter of tubes increases the rates of heat transfer. However, on the other hand, it increases the pressure drop. An effort has been made to find a golden mean by the use of “microchannels” of appropriate hydraulic diameter for single-phase applications in radiators. The work comprises parametric analysis to study the effect of microchannel diameter on heat transfer and fluid pressure drop. Elaborating this, an analysis was performed by the means of analytical procedure and computational methods using Ansys CFX, the data generated indicates that the Nusselt Number is very large, in hundreds, as compared to the conventional channels. The overall HTC is in the range of 2000 W/m2 K indicating that the radiator size can be reduced by 40% for the same rate of heat transfer for 0.001 m hydraulic diameter. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.