Synergistic effect for the mixtures of polyglycerol esters of fatty acids (PGEFs) [including triglycerol diisostearate (TGDIS), pentaglycerol distearate (PGDS), triglycerol monostearate (TGMS) and triglycerol monooleate (TGMO)] with sodium oleate solubilizing water in gasoline has been investigated. The effect of a series of alcohols on the water amounts solubilized in the microemulsion systems of TGDIS/sodium oleate/alcohol/gasoline/water has been studied. It was shown that the microemulsion system of TGDIS/sodium oleate/ 1-butanol/gasoline/water exhibited better behavior in solubilizing water than the other systems studied. The best weight ratio of TGDIS/ sodium oleate was 6:4, in which the maximum solubilization capacity of water was 2.402 g at 16 degrees C, when the amount of the mixed surfactants and gasoline were 0.740 and 6.000 g respectively. In addition, the microemulsion system of TGDIS/sodium oleate/1-butanol/ gasoline/water was more water soluble and less temperature sensitive, in comparison with the microemulsion system of TGDIS/lauryl polyoxyethylene (9) ether (AEO(9))/gasoline/water. (c) 2006 Elsevier Ltd. All rights reserved.