Microchannels have been used in electronics cooling and in air conditioning applications as condensers. Little study has been made in the application of microchannels in automotive heat exchangers, particularly the radiator. The presented research captures the need for the design improvement of radiator heat exchangers in heavy-duty vehicles in order to reduce aerodynamic drag and improve fuel economy. A method for analyzing an existing radiator is set forth including the needed parameters for effective comparisons of alternative designs. An investigation of microchannels was presented and it was determined that microchannels can improve the overall heat transfer of a radiator but this alone will not decrease the dimensions of the radiator. Investigations into improving the air-side heat transfer were considered and an improved fin design was found which allows a reduction in frontal area while maintaining heat transfer. The overall heat transfer of the design was improved from the original design by 7% well as 52% decrease in frontal area but at the cost of 300% increase in auxiliary power. The energy saved by a reduction in frontal area is not substantial enough to justify the increase of auxiliary power. The findings were verified through a computational fluid dynamic model to demonstrate the heat transfer and pressure drop of microchannel tubes. The results confirmed that heat transfer of microchannels does improve the thermal performance of the radiator but the pressure drop is such that the net benefit does not outweigh the operating cost. An additional CFD study of the new fin geometry and air-side heat transfer predictions was conducted. The results of the study confirmed the theoretical calculations for the fin geometry.