The first comparison is made of molecular dynamics (MD) simulation and experimental self-diffusivities for a binary mixture adsorbed inside a zeolite. MD results for methane/tetrafluoromethane mixtures in silicalite agree well with self-diffusion coefficients from pulsed field gradient NMR. At constant total loading, the diffusivities of both components decrease as the fraction of the larger, less-mobile CF4 in the system is increased. Singlet and pair distribution functions were also calculated. The simulations predict preferential adsorption of CF4 in the straight channels and methane in the zigzag channels.