Calculation of viscosities of colloidal systems via molecular dynamics simulations can be done, e.g., with the help of the Stokes-Einstein formula. In this paper we use the method proposed by Palmer and implemented in GROMACS 2020 software package for estimating the viscosities of one- and two- component
molecular liquids. This method is based on computation of the autocorrelation
functions of the momentum. It has been here applied for finding the viscosities of several homogeneous molecular systems (water, pentane, heptane, decane) and that of a weakly inhomogeneous system, i.e., a small premicellar aggregate of non-ionic surfactant molecules (C12E4) in heptane.