This work aims at enhancing the thermal conductivity of base fluids (water and methanol) through successive washing of polymers from the surface of polyvinylpyrollidone (PVP)-stabilized copper (Cu) nanoparticles. Cu nanofluids were successfully synthesized and characterized using transmission electron microscope and UV–vis spectrophotometer. Thermal conductivity of freshly prepared Cu nanofluid shows ~10% enhancements. The poor enhancement in thermal conductivity is due to the presence of thick polymer coating on the surface of nanoparticles. A new technique has been developed to erode the polymers from the nanoparticle surface by repeated washing and redispersion. After one-time washing and redispersion, the thermal conductivity of nanofluid has been increased to 0.732 W/mK (~22% enhancements). Greater enhancement (~30.34%) has been achieved after three times continuous washing and redispersion. Finally, the experimental values of thermal conductivity were compared and validated against the existing Maxwell effective model. © 2020 Curtin University and John Wiley & Sons, Ltd.