In this study experimental densities and viscosities, at temperatures to 530 K and pressures to 70 MPa, are reported for mixtures of toluene +11.3 mol% and 32.4 mol% ethylene and for mixtures of toluene +7.9 mol% and 30.7 mol% propylene. Both densities and viscosities are measured simultaneously using a variable-volume, rolling ball viscometeridensimeter apparatus. Mixture viscosities decrease as the ethylene or propylene mole fraction increases. The expanded experimental uncertainties in the reported viscosities and densities, both at 95% confidence level, are estimated to be 4.0% and 0.8%, respectively. Mixture viscosities and densities are fit to Tait-like expressions, with temperature dependent parameters, to provide a facile method for data interpolation. The Perturbed Chain, Statistical Associating Fluid Theory equation of state (PC-SAFT EoS) is used to predict mixture densities to within 3.0% using literature values for the PC-SAFT pure component parameters from fitting both vapor pressure and saturated liquid densities. The Free Volume Theory model, with PC-SAFT calculated densities as input, reproduces the viscosities for the four different mixtures with maximum deviations of 13.5% and 15.4% for ethylene + toluene and propylene + toluene mixtures, respectively. (C) 2019 Elsevier B.V. All rights reserved.