In this work, the porous media flow of solutions of mixtures of Poly(ethylene oxide), PEG, and Sodium Dodecyl Sulfate, SDS, was studied. Aqueous solutions of PEO exhibited the well known critical extension thickening effect when flowing through disordered packings of glass spheres. Upon addition of SDS to a solution of fixed PEO concentration, the extension thickening of the mixture exhibits a maximum as a function of SDS concentration that mimics the shear viscosity behavior of the polymer-surfactant mixture. However, when NaCl is added to the mixture, higher extension thickening effects at relatively low SDS concentrations were detected, in spite of the fact that the shear viscosity of the mixtures was about the same as that of equivalent PEO/SDS solutions in deionized water. The results were rationalized in terms of how the formation of SDS micellar aggregates along the PEO chain can alter the ability of the polymer to form transient entanglement networks, which is the cause of the extension thickening behavior.