Experimental data are reported on liquid-liquid equilibrium in saturated hydrocarbon - C-6-C-8 arene - mixed extractant (triethylene glycol-sulfolane-water) pseudoternary systems of varying composition at 50 degrees C. It was shown that increasing the sulfolane: TEG ratio from 21.7:78.3 to 60:40 changes the character of the bimodal curve in the phase diagram from the open to the closed type. As a result, for the same ratio of extractant and feedstock, all of the extraction indices - the degree of extraction, distribution coefficients, and arene content in the extractant - improved and the hydrocarbon fractionation factors increased.