The cross second virial coefficients and dilute gas shear viscosities, thermal conductivities, and binary diffusion coefficients of the systems (CO₂ + C₂H₆) and (H₂S + C₂H₆) were determined with high accuracy at temperatures from (150 to 1200) K by means of statistical thermodynamics and the kinetic theory of polyatomic gases. The required intermolecular potential energy surfaces (PESs) for the CO₂-C₂H₆ and H₂S-C₂H₆ interactions are presented here, while the like-species interactions were modeled employing PESs developed previously as part of our studies on the pure gases. All PESs are based on high-level quantum-chemical ab initio computations and are represented analytically by site-site potential functions. The agreement between the calculated values for the investigated mixture properties and the few reliable experimental data is very satisfactory.