The difference between the experimental thermophysical properties of nanofluids and the values obtained by ideal mixture theory was investigated. It is shown that by ignoring fluid adsorption around nanoparticles in a nanofluid, ideal mixture theory underestimates the density, thermal conductivity, and viscosity and overestimates the heat capacity and thermal expansion coefficient of the nanofluids. Dependency of these deviations upon the adsorption of nanofluid molecules on the surface of nanoparticles was investigated and a linear correlation was observed at different temperatures, concentrations, and nanoparticle diameters. The excess adsorption of the nanofluid molecules is obtained by using an accurate version of the density functional theory. (C) 2016 Elsevier Ltd. All rights reserved.