The dynamic viscosity and density of two hydrocarbon mixtures representative of some heavy petroleum distillation cuts at 515 K have been studied in the temperature range 293.15-353.15 K and up to 100 MPa. The pure hydrocarbons used are n-tridecane, 2,2,4,4,6,8,8-heptamethylnonane, heptylcyclohexane, heptylbenzene, and 1-methylnaphthalene. The normal boiling point of these five compounds are 508.0, 513.1, 518.1, 519.1 and 515.0 K, respectively. The studied mixtures contain respectively three hydrocarbons (n-tridecane, heptylcyclohexane, heptylbenzene) and five hydrocarbons.The viscosity was measured with a falling-body viscometer, except at atmospheric pressure, where a classical capillary viscometer was used. The experimental uncertainty for the dynamic viscosity is 2%, except at atmospheric pressure, where the uncertainty is 1%. For the density, the uncertainty is less than 1 kg m(-3). The viscosity data obtained for the two mixtures (84 experimental points) have been used to evaluate the performance of seven different representative models, applicable to hydrocarbon fluids, incorporating the effects of temperature, pressure and composition. The evaluated models are based on the classical mixing laws, the self-referencing model, the hard-sphere scheme, the free-volume viscosity model, the friction theory, and the Lohrenz-Bray-Clark (LBC) correlation. It follows from the discussion that some of the schemes are able to predict the viscosity of these two mixtures being simple representations of some petroleum distillation cuts at 515 K. This work shows the potential extension of these viscosity approaches to real petroleum fluids.In addition, using the experimental densities, the variation of the internal pressure versus temperature and pressure for the two synthetic hydrocarbon mixtures has been evaluated. (C) 2003 Elsevier B.V. All rights reserved.