The vapour-liquid critical properties of binary mixtures are calculated using conformal solution theory, the one-fluid model, the van der Waals and Carnahan-Starling-van der Waals equations, and a new Dieterici-type equation of state reported recently [J. Chem. Phys. 115 (2001) 371]. Comparisons with experimental data are reported for the critical properties of n-alkane mixtures ranging from methane to n-octane. A common feature of these comparisons is that the new Dieterici-type equation of state yields good prediction of the pressure-temperature critical locus without the need to use arbitrary adjustable parameters in the combining rules for mixture properties. In particular, the Dieterici-type equation correctly predicts the maximum in the pressure-temperature curve. In contrast, the van der Waals-type equations are inaccurate. Dieterici-type equations of state may have a useful rule in the prediction of fluid phase equilibria by reducing the need for adjustable parameters in the combining rules. (C) 2003 Elsevier B.V. All rights reserved.