A study was carried out on aspects of phenomena on the interfacial boundary of acids and hydrocarbon systems of different complexity. These phenomena were evaluated relative to the interfacial tension measured by the pendant drop method. We discovered peculiarities of the interaction of hydrochloric and sulfamic acids with individual hydrocarbons as well as complex hydrocarbon systems. The complex dependence of the interfacial tension on the composition and properties of the hydrocarbon phase, type and concentration of the acid, and the chemical composition of asphaltenes was elucidated.