The use of 2,2,4-tri methyl pentane as a cosolvent for extraction of aromatic hydrocarbons from tube cut is studied. Optimized values of extraction temperature and amount or 2,2,4-tri methyl pentane are determined. The liquid-liquid equilibrium between {lube oil + furfural + cosolvent} is examined with the NRTL equation, The binary interaction parameters for the NRTL model are obtained by minimization of an objective function. General binary interaction parameters are computed and reported for estimating the liquid-liquid equilibrium products between 323.1.5 and 343.15 K. Also, a generalized model is presented for calculation of the refractive index and specific gravity of tube-oil fractions. The calculated results are in good agreement with the results of the experiments.