An experimental study was carried out on the viscosity of ethylene glycol (EG)-based nanofluids containing Al2O3

ZnO and CuO nanoparticles with the particle concentrations of 0.5%/3.0%/5.0%/7.0% (mass)

respectively. Nanofluid samples were prepared by the two-step method without adding surfactant. The relative viscosity of EG-based nanofluids was not a strong monotonous function of temperature within 30-60℃. Nevertheless

the relative viscosity of EG-based nanofluids fluctuated with increasing temperature when mass fraction was high enough

with the fluctuation of ZnO (elongated)-EG nanofluid being more significant. It was also found that the relative viscosity of all the nanofluids tested increased with increasing volume fraction. Among them

CuO-EG increased most intensely while Al2O3-EG increased most moderately. Finally

a comparison analysis was made between the present experimental data and the prediction equations in literature.