Predicting oil-in-water emulsion droplet size and stability in turbulent flow is useful for choosing separation processes in heavy oil extraction. In order to study the process, averaged droplet sizes for toluene, n-heptane and mineral oil were measured during stepped-down turbulent mixing. Droplet sizes were measured for five concentrations of heavy oil in toluene at oil fraction 0.05 in model process water as a function of time during turbulent mixing. Mixing was conducted with a Rushton turbine in a cylindrical tank. Size distributions were measured with the Mastersizer 2000 laser diffraction instrument. Dynamic interfacial tensions sigma(dyn) (by drop volume technique, DVT) and static interfacial tensions sigma (by du Nouy ring) as a function of time were measured. Data were fitted with two adsorption kinetic models (diffusion limited D1, and Langmuir based Lb) to find "equilibrium" interfacial tensions sigma(E) needed to predict Sauter mean diameter d(32) in Hinze-Kolmogorov (H-K) and Wang-Calabrese (W-C) models. Data were also analyzed by using a classical breakage-coalescence kinetic model. Results showed that by using u(dyn) with W-C model the predicted d(32) changed proportionately with sigma(dyn). For any sigma(E) the d(32) predicted using the W-C model was closer to the experimental d(32) than the d(32) predicted by the H-K model. The UE,s obtained by the DI and Lb models were similar when fitted to DVT data giving identical W-C predicted d(32). However, only the D1 model fitted the a-time data obtained by the du Nouy ring technique and the sigma(E) in W-C model gave d(32) closest to experimental d(32) for droplets of 1-10wt% heavy oil in toluene. The predicted d(32) of droplets for the 25-wt% heavy oil was larger than the experimental d(32). This difference was attributed to interfacial film thickness and decreased elasticity discussed in an earlier publication. Crown Copyright (c) 2006 Published by Elsevier Ltd. All rights reserved.