In the lubricating oil manufacturing process, the aromatic content of these products is reduced by solvent extraction. In this work, a thermodynamic model is developed to simulate the properties of these mixtures when liquid-liquid equilibrium (LLE) is established with a suitable solvent. The mixtures involved in the extraction process (feed, raffinates, and extracts) are considered to be a mixture of three types of components: saturates (S), aromatics (A), and polars (P). Pseudo-components were characterized by two properties: the average boiling point obtained from the distillation curve and the specific gravity. LLE was described by means of the nonrandom two-liquid (NRTL) model with temperature-dependent interaction parameters. The use of only three pseudo-components leads to a reduced number of interaction parameters to be determined by correlation of the available experimental equilibrium data. Calculated and experimental compositions and yields of the raffinates and extracts were compared, and good agreement was obtained.