The invention relates to a method for producing tertiary crude oil with the aid of a surfactant mixture and/or to the use of a surfactant mixture for producing tertiary crude oil by means of Winsor type III microemulsion flooding, in which a surfactant mixture is forced through at least one aqueous injection well into a mineral oil deposit and crude oil is removed from the deposit through at least one production well. The surfactant mixture comprises, for lowering the interfacial tension between oil and water to < 0,1 mN/m, at least the following components: (a) one or more polycarboxylate(s) containing at least 50 mol.% acrylic acid units and/or methacrylic acid units and/or maleic acid units and/or itaconic acid units or salts thereof, and (b) one or more anionic and/or non ionic surfactant(s).