Determination of stability of high-viscosity marine fuel from the point of colloid chemistry concept of oil disperse systems and the need for inclusion of this parameter in the current requirements are expounded. High-viscosity marine fuels produced from residual fuel oil, visbreaking residue, and catcracking light gas oil were taken as the objects of the study. The stability of the obtained samples was determined via xylene equivalent. Also determined was the effect of dispersing additives based on hydroxyethylated amines and alkyl naphthalenes on the stability of the obtained samples of high-viscosity marine fuels.