The stability of four components emulsions - oil, water, surfactant and cosurfactant - is examined. From a series of stable formulations, prepared with one surfactant family, the correlations between different characteristic parameters - solubility parameters of the oil and of the cosurfactant, surfactant HLB, required HLB of the oil - are checked. The experimental study displays linear relations between some of these parameters. The results allow to predict that the choice of the oil induces the choice of an HLB range for the surfactant and a solubility parameter range for the cosurfactant.