Microchannel heat exchangers (MHEs) have become a leading candidate for applications demanding removal of highly concentrated heat, including cooling of future generation high-performance microelectronic and power-electronic modules. Metal-based MHEs offer potential advantages over silicon-based counterparts in terms of overall heat transfer performance and mechanical robustness. Low-cost fabrication of metal-based MHEs and quantitative evaluation of their liquid flow and heat transfer characteristics are essential for establishing the technical feasibility and economic viability of such devices. Adoption of metal-based MHEs in many applications demands quantification of liquid flow and heat transfer performance with application-relevant coolants, for example, ethylene glycol (EG)/water mixtures rather than pure water. As a first step in this direction, we report here fabrication and assembly of all-Cu MHE prototypes, as well as results of flow and heat transfer testing using pure water and pure EG as the liquid medium. Results of heat transfer testing indicate sensitivity of overall heat transfer performance to entrance length effects. In the case of pure EG, the thermal entrance length is significantly influenced by its Prandtl number value under different testing conditions. Varying testing conditions led to differences in the Prandtl number, and consequently the heat transfer performance.