Numerical investigations are performed to explore the aluminum trapezoidal microchannel heat sink (MCHS) cooling benefits by using different types of base nanofluids for laminar flow. Considering a diamond nanoparticle with particle volume fraction of 2% was mixed in four different base fluids including water, ethylene glycol (EG), oil, and glycerin. The threedimensional steady, laminar flow and heat transfer governing equations are solved using the finite volume method. The computational domain is taken as the entire heat sink including the inlet/outlet ports, wall plenums, and microchannels. The impact of different types of base fluids in these four mixture flows on the microchannel temperature profiles, heat transfer coefficients, pressure gradients, friction factor, and thermal resistance were examined. It is found that the best uniformities in heat transfer coefficient and temperature among the four mixture flows for diamond nanoparticle can be obtained in MCHS using glycerinbase nanofluid followed by engine oil-base nanofluid, EG-base nanofluid, and water-base nanofluid. It is found that, the use of high-Prandtl number base fluid such as glycerin is preferable and can be recommended to maximize the merits of adding nanoparticles for MCHS performance.