High solubilization capacities and ultra-low interfacial tensions between water and oil are among the most important properties of microemulsion systems. So-called “extended surfactants” enable a very efficient solubilization of various oils, including triglycerides [1] [2]. Via systematic phase behavior studies of (pseudo-)ternary microemulsion systems, we were able to completely solubilize equal volumes of water and n-octane with only 2 wt.% of a highly efficient anionic surfactant mixture of an alkyl alkoxy sulfate (“extended surfactant”) and alkyl benzene sulfonate. Although solubilization of a medium-chain triglyceride proved somewhat less efficient compared to n-octane, it was feasible to formulate a symmetrical microemulsion using only 7 wt.% of the surfactant mixture, making it significantly more efficient than conventional alkyl polyglycol ethers [3]. However, this type of very efficient extended surfactants was only partly biobased and the alkyl benzene sulfonate was fully fossil based. To increase the content of fully biobased surfactants and to obtain at the same time a good solubilization rate for triglycerides, we combined the extended surfactant with surfactants already used in washing applications, such as a combination of nonionic alkyl polyglycol ethers and anionic alkyl benzene sulfonates and alkyl ether sulfates. Systematic investigations of the temperature-dependent phase behavior and electrical conductivity allowed us to stepwise replace the alkyl alkoxy sulfates. Thereby, we succeeded in compensating the large hydrophilicity of alkyl ether sulfates by adding small amounts of a fully biobased long-chain mono- and diglyceride mixture, resulting in an efficient solubilization of medium-chain triglycerides in microemulsions.