Modification of physical and mechanical properties of soils under oil pollution has been researched by N.N. Brakorenko, T.Ia. Emel’ianova, А.P. Kazennikov, Iu.N. Kopylov, Iu.A. Nefed’eva, V.V. Seredin, M.R. Iadzinskaia, L.V. Shevchenko, I.V. Shirshova and others. Many aspects of modification of physical and mechanical properties polluted by hydrocarbons have not been studied in detail, with results being sometimes controversial. For instance, one of the leading factors conditioning physical and mechanical properties of soils is the size of structural elements. However, particle aggregation in clay soils polluted by hydrocarbons has been studied insufficiently. Thus, the present research is focused on quantitative effects of hydrocarbons on aggregative capacity of soils. For a statistical justification of the influence of microaggregate soil composition on oil pollution degree correlation diagrams of oil pollution degree versus microaggregate soil composition were generated, correlation coefficients were calculated. The analysis was performed separately for clay, loam and clay sand. The experiments found that the oil pollution degree in clays depends on their fractional composition. In loam and clay sand such regularity was not found. In clays aggregation takes place mostly in a clay fraction, in loams it is observed in clay and silt fractions, in clay sands it occurs in silt fraction. The processes of aggregation are the most intensive in clays. It is determined by particle surface energy value.