The pressure and temperature dependence of the stabilization vs dissociation yield of chemically activated ethylbenzene ions from the charge-transfer reaction O-2(+) + C8H10 --> O-2 + C8H10+ is analyzed. Combining the measured data with experimental specific rate constants, k(E), for dissociation of ethylbenzene ions from the literature allows absolute values of the product Z for energy transfer in the buffer gases He and N-2 to be derived. By assigning the collision frequency Z to the Langevin rate constant, the average energies transferred per collision for highly excited C8H10+ are obtained. They are close to the corresponding values for neutral alkylbenzenes. k(E) shows a transition from values given by phase space theory at low energies to values arising from an anisotropic valence potential at higher energies. The charge transfer process is analyzed in terms of resonant charge transfer, charge transfer through ethylbenzene-O-2(+) complexes, and charge transfer producing electronically excited O-2 molecules, with the former being exploited for the described study of collisional energy transfer.