Micro-explosion is caused by the sudden vaporization of water drops inside water-in-oil emulsion. Past studies have shown an optimal diameter for dispersed water. This optimal micro-explosion produces the largest number of secondary droplets, i.e. the largest interfacial area among the resulting spray. Such an increase in the interfacial area within the spray causes a better and less polluting combustion process. By using an infra-red camera, the present experiments can measure the size and planar velocity of secondary droplets issued from an optimal and also a non-optimal emulsion. The distributions of kinetic energy and surface energy among the spray are then calculated and discussed. Among the secondary droplets, it results that the optimal micro-explosion favors surface energy over kinetic energy. (C) 2016 Elsevier Masson SAS. All rights reserved.