The Green-Kubo method for calculating viscosities at zero-shear rate of liquid alkanes by means of molecular dynamics (MD) has been applied. Within this thesis, the common study of simulating viscosities close to ambient pressure has been extended to pressures relevant for studies of elastohydrodynamic lubrication (0.1 to 1000MPa). Furthermore, attempts have been made to elucidate the influence of the chemical structure on the high-pressure rheology of \textit Roelands' pressure viscosity relation. Analysis of different contributions to the pressure tensor showed that in contrast to the normal alkanes, the pressure tensor contribution due to bonds dominates over the angle contributions in branched alkanes. Finally, it was also found that when the Green-Kubo method is applied to systems with long relaxation times, significant computational efforts are necessary to obtain statistically reliable results.