The density and viscosity of binary 1-hexene + 1-octene mixtures have been simultaneously measured over the temperature range from (298 to 470) K and at pressures up to 196 MPa using a hydrostatic weighing and falling-body techniques, respectively. The measurements were made for three concentrations of 0.200, 0.429, and 0.692 mole fraction of 1-octene. The combined expanded uncertainty of the density, pressure, temperature, and viscosity measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be (0.15-0.30) %, 0.05%, 0.02 K, and (1.5-2.0) %, respectively, depending on temperature and pressure ranges. The measured densities and viscosities were used to calculate the excess molar volumes and viscosity differences. It is shown that the values of excess molar volume for 1-hexene + 1-octene mixtures are negative, while the viscosity differences are mostly positive at all measured temperatures and pressures over the whole concentration range. The measured densities and viscosities were also used to develop a Tait-type equation of state and viscosity correlation model for liquid 1-hexene + 1-octene mixtures. Theoretically based Arrhenius-Andrade and Grunberg and Nisan type equations were used to represent the temperature and concentration dependences of the measured viscosities for liquid 1-hexene + 1-octene binary mixtures at atmospheric pressure. (C) 2014 Elsevier B.V. All rights reserved.