Saturated, aromatic, resin, and asphaltene (SARA) group and fractional composition of 14 samples of marine residual fuel oils and components suitable for their production is studied. Analysis of the results of laser Fourier-difractometric study of solutions of these samples in isooctane made it possible to develop a quantitative method of assessment of their colloidal stability. Correlative relationships of the composition and colloidal stability of the studied asphaltene-containing and asphaltene-free petroleum products are derived. The inapplicability of the term "straight-run" for assessment of colloidal stability of residual fuels is shown experimentally.