Recently, a comprehensive experimental study of the viscosity up to 100MPa has been carried out on the ternary system composed of methylcyclohexane, cis-decalin, and 2,2,4,4,6,8,8-heptamethylnonane in order to provide data for asymmetrical hydrocarbon mixtures. Although not as complex as real petroleum fluids, the studied system is of interest for the evaluation of viscosity models for their potential application to the simulation of complex fluids with an asymmetrical molecular distribution. The measured data (1554 points) have been used in an extensive evaluation of the performance of seven different viscosity models applicable to hydrocarbon fluids. These models range from empirical correlations, such as the self-referencing model and the commonly used LBC model in petroleum engineering, to recent approaches with a physical and theoretical background, such as the hard-sphere scheme, the free-volume model, and the friction theory. This comparative study shows that the evaluated models, except the LBC model, can represent the viscosity of the ternary system within an acceptable uncertainty for most engineering applications. However, the extension to real reservoir fluids may be more appropriate for some of the models, such as the free volume and the friction theory, since these models are not limited to liquids and dense fluids, but are also applicable to gases, which is a required feature within the oil industry. (C) 2004 Elsevier B.V. All rights reserved.