This paper is focused on the study of the viscous flow behaviour of blends of polyethylene and Vacuum Gas Oil (VGO) under dynamic shear. The application of different models for the prediction of the shear viscosity under different industrial operating conditions of shear rates, temperature and base components weight fractions has also been investigated. Viscosimetry measurements of the blends with different polymer fractions between 0 and 10 % wt., temperatures between 333 K and 433 K at shear rates up to 10000 1/s were performed. These blends were shown to have peculiar flow behaviour: exhibiting Newtonian fluid flow property at higher temperatures and lower polymer concentrations, while at lower temperatures and at higher polymer concentrations, showing non-Newtonian shear thinning or pseudo-plastic behaviour. These properties have been shown to be more pronounced at lower shear rates than at higher shear rates. As for the prediction of the blends shear viscosity under simultaneous varying shear rate, polymer weight fraction and temperature changes, a very good fit of the experimental viscosimetry data to the proposed unified Sisko-Arrhenius model has been obtained, especially considering the high number of experimental data fitted and model parameters simultaneously optimised.