We investigate the properties and phase behavior of the water-diesel fuel-Neonol AF 9-6/2-ethylhexanol system, which is regarded as a promising microemulsion fuel. A pseudoternary diagram of the system has been obtained. In the diesel fuel/water (DF/W) ratio ranging from 98:2 to 50:50 and the emulsifier concentration of 8-40 vol %, a region of microemulsions has been distinguished, generating particular interest as an alternative fuel. In the region under study, a reverse micellar phase L-2 has existed predominantly. Fish-cut diagrams have been obtained for the DF/W ratios in the emulsifier concentration-temperature coordinates. An increase in the water fraction in microemulsions significantly has narrowed the range of their stability. The critical changes of microemulsion properties have been identified using the fish-cut diagrams. We have established the empirical relationship among the phase inversion temperature, the emulsifier concentration in the phase inversion point, and the water fraction in microemulsions.