Some common volume-independent mixing rules and the problems associated with them are reviewed. Reported experimental data of a highly non-ideal quaternary mixture and all its constituent binaries and ternaries are used for adjusting binary interaction parameters and comparing the performance of each mixing rule in predicting vapor-liquid equilibria (VLE). The parameters in each mixing rule were obtained fitting experimental binary data only. The ternary and quaternary VLE calculations were then used to test the capability of the mixing rules to predict multicomponent VLE. It is shown that the VLE of those systems can be adequately reproduced with a cubic equation of state using Wong and Sandler’s mixing rule with Wilson’s excess Gibbs energy function thanks to its simultaneous correction of several inconveniences. It is also shown that mixing rules should be tested with multicomponent mixtures.