Liquid−liquid equilibria (LLE) of alkane + aromatic + solvent systems is of interest in connection with the extraction of aromatics from petroleum fractions, for example, naphtha, distillates, lube oil, and so forth. Though the actual industrial systems contain a large number of compounds, LLE studies on a smaller number of representative compounds are also important in the development of theoretical/semiempirical LLE models for use in the design of extraction processes. In the present work LLE data has been experimentally obtained for the ternary systems heptane + benzene + furan-2-carbaldehyde (furfural) and heptane + methylbenzene (toluene) + furfural at two temperatures (298.15 and 303.15) K, and for the quaternary systems heptane + dodecane + benzene or toluene + furfural at 298.15 K. The data are seen to be correlated excellently by the nonrandom two-liquid model. The model parameters were determined by data regression using the Nelder−Mead optimization technique. The model also enabled tie line calculations between the last experimental tie line and the plait point, thereby giving the shape of the full two-phase region.