Computer simulations of the n-heptane + perfluoro-n-hexane system is used to understand the unusual behaviour of the horizontal inflection of the vapour-liquid interfacial tension experiments of alkanes-perfluoroalkanes mixtures. Simulations are conducted and good agreement with experiments is obtained. From the results a change in curvature to a nearly constant value in the tensions at high perfluoro-n-hexane compositions is identified. Dynamic, thermodynamic and structural properties are analysed in that region and peculiar tendencies of those properties are found which help us to understand the nature of the uncommon inflection in the isotherms. (C) 2015 Elsevier B.V. All rights reserved.