The use of the INSEDELF method to measure solid-liquid phase separation was extended to water/diesel fuel emulsions to study liquid-liquid phase separation. We have demonstrated that this method is a pertinent tool for characterising the stability of these emulsions and for optimising complex formulations intended for winter use of these fuels. It permitted determination of the optimal content of antifreeze in the aqueous phase. A similar optimisation can be carried out on the diesel fuel phase. The INSEDELF method now constitutes a method that can be used in research to develop new emulsions and anti-settling additives as well as to control the fabrication of these different products. (C) 2004 Elsevier Ltd. All rights reserved.