The viscosity model based on corresponding states used in this work was originally published by Pedersen et al. with further improvements published by Pedersen and Fredenslund. Adaptations to include better estimates for heavy oils were originally published by Lindeloff et al.. The corresponding states principle was firstly introduced in the thesis of Johannes Diderik van der Waals in 1873 and this subject was published later by him again in another article . In the scope of viscosity calculations, it can be used to provide a scale-factor that allows the calculation of a multi-component mixture viscosity from an accurate correlation for a single component fluid. This is done by assuming that the reduced viscosities of any two fluids at the same reduced must be equal . Thus,