In a recent publication (D'Agostino el al., 2011) a simple equation was proposed to predict mutual diffusion coefficients in binary liquid mixtures close to the consolute point, from the tracer diffusivities and thermodynamic data. This equation is based on dynamic concentration fluctuations as predicted by the critical point theory, driven by chemical potential. Here literature data for 14 mixtures not exhibiting a consolute point is used to test the same predictive equation for the more general case of non-ideal binary liquid mixtures. The agreement is found to be excellent for 13 of the 14 systems, certainly within the accuracy of the available data. The exception, acetone-chloroform, is an associating mixture exhibiting a negative deviation from Raoult's law; the anomalous behaviour may simply be a result of experimental errors, but could alternatively be accounted for on the basis that strong compound formation means that the tracer diffusivities cannot in this case be identified with the molecular mobilities of each species. This suggests that dynamic concentration fluctuations may occur in liquid mixtures well away from the consolute point, even in systems not exhibiting one at all, and that the behaviour of these fluctuations is governed by the variation of chemical potential with composition in the liquid mixture. The ability to predict mutual diffusion coefficients from tracer diffusivities has significant practical implications for situations where conventional measurement of the mutual diffusion coefficient is difficult or impossible. The ease and accuracy of measurement of tracer diffusivities has increased enormously in recent years, including in a number of in situ situations, using pulsed field gradient NMR, now a widespread and routine technique. (C) 2011 Elsevier Ltd. All rights reserved.