Accurate values for the cross second virial coefficients and dilute gas shear viscosities, thermal conductivities, and binary diffusion coefficients of the (CH4 + C3H8) and (CO2 + C3H8) systems were determined at temperatures from (150 to 1200) K using state-of-the-art computational approaches. The cross second virial coefficients were calculated semiclassically using the Mayer-sampling Monte Carlo method, while the transport properties were computed by means of the classical trajectory approach in conjunction with the kinetic theory of molecular gases. The required intermolecular potential energy surfaces (PESs) for the CH4-C3H8 and CO2-C3H8 interactions are reported in this work, whereas those for the CH4-CH4, CO2-CO2, and C3H8 -CH8 interactions were taken from our previous work on the pure gases. All PESs are based on high-level quantum-chemical ab initio calculations and were fine-tuned to the best experimental data for the second virial and cross second virial coefficients. Overall, the agreement of the calculated thermophysical property values with the few available experimental data is satisfactory.