Liquid-liquid equilibria for methanol + n-alkanes (C-9 to C-12) were determined in the temperature range (278.15 to 308.15 K), using a visual static method. Densities, refractive indices, and speeds of sound were also measured at 288.15, 298.15, and 308.15 K for acetone + n-alkane mixtures and at 298.15 and 308.15 K for methanol + n-alkane mixtures to study the temperature influence on mixing phenomena. The results were used to model liquid-liquid coexistence and derived properties trend. The calculated values based on the UNIQUAC equation were found to be similar to those based on the NRTL model,. The Prigogine-Flory-Paterson theory was applied to estimate the excess molar volumes and the UNIFAC group contribution model for phase equilibria.