We have performed molecular dynamics simulations to study structure and equilibrium properties of liquid-vapor interfaces of binary mixtures containing argon and methane over the entire range of compositions. The phase equilibrium data obtained from our simulations are compared with those from NpT+ test particle calculations of an analogous system. Values of the surface tension were computed and extrapolated to the full Lennard-Jones potential using a new ansatz to determine tail contributions to the surface tension directly within the simulation run. This new method uses the actual partial density profiles obtained within the simulation and, therefore, does not require any prescribed functional form. From both the surface tension results and the partial density profiles the relative enrichment of argon at the interface was estimated.