In this work we combine two recently proposed computer simulation techniques: the wandering interface method for the calculation of surface tensions and Janecek's method for the estimation of long-range dispersive interactions to predict the surface tension of ethane. We have obtained results for two well-known models, the transferable potentials for phase equilibria (TraPPE) and optimized potentials for liquid simulations (OPLS) force fields. We show that neglecting long-range contributions to the dispersive energy as it is often done may yield surface tensions that are far too low by as much as 40%. Such contributions can be effectively accounted for, however, and the resulting liquid-vapor coexistence densities and surface tensions show a rather good agreement for the TraPPE model, but quite less so for the OPLS model.