mixed surfactant system of sodium dioctyl sulfosuccinate (AOT), alkyl diphenyl oxide disulfonate (ADPODS) and sorbitan monooleate (Span 80) was shown to form Winsor type I and type III microemulsions with hexadecane and motor oil. In addition, high solubilization and low interfacial tension were obtained between the oils and surfactant solutions both in the supersolubilization region (Winsor type I system close to type III system) and at optimal conditions in a type III system. In the present study, this mixed surfactant system was applied to remove oily soil from fabric (a polyester/cotton blend), and detergency results were correlated to phase behavior. Dynamic interfacial tensions were also measured between the oils and washing solutions. In the supersolubilization and in the middlephase regions (type III), much better detergency performance was found for both hexadecane and motor oil removal than that with a commercial liquid detergent product. In addition, the detergency performance of our system at low temperature (25°C) was close to that obtained at high temperature (55°C), consistent with the temperature robustness of the microemulsion phase behavior of this system. Paper no. S1362 in JSD 6, 205-214 (July 2003).KEY WORDS: Detergency, dynamic interfacial tension, microemulsion, mixed surfactants, supersolubilization.Detergency, by definition, is the removal of unwanted substances, so-called soils, from a solid surface by contacting them with liquid (1). In this complex process, soil removal is dependent on several factors, such as the nature and composition of the washing solution, type of soil, hydrodynamic conditions, water hardness, temperature, and electrolyte level, as well as the nature of the solid surface. Interactions at the air-water, liquid-liquid and liquid-solid interfaces are involved (2). FIG. 4. Detergency performance for hexadecane (A) and motor oil (B) removal for our formulation (3% AOT, 2% ADPODS and 2% Span 80) at 25°C, 0.112% active surfactant concentration, and various salt concentrations compared with deionized water and commercial liquid detergent (CP), SPS is our formulation in the supersolubilization region, and S* is the optimum salinity at equilibrium, from phase studies. For other abbreviations see Figure 1. FIG. 5. Hexadecane removal with our formulation compared to CP and to the IFT between the oil and washing solution at various salt concentrations.FIG. 8. Comparison of detergency performance of our microemulsion-based formulation of 3% AOT, 2% AD-PODS, and 2% Span 80 at supersolubilization [5 and 12% NaCl with hexadecane (A) and motor oil (B), respectively] with liquid detergent (CP) at different active concentrations (wt% of total surfactants in solution).