Quasiclassical trajectory analysis of oxygen dissociation is presented with conditions sampled from thermal equilibrium and nonequilibrium. Ground state O2 + O2 and O2 + O interactions both occur on several degeneracies, and so a total of 13 potential energy surfaces are used in the investigation. Spin and spatial degeneracy is found to have a moderate effect on the dissociation rate, and a strong effect on vibrational relaxation mechanisms in O2 + O. For a given thermal environment, the oxygen dissociation rate is found to be similar for all collision partners. The vibrational energy decrease due to dissociation, a necessary input to CFD, depends on the degree of thermal nonequilibrium, and a curve collapse with previous data for nitrogen dissociation is demonstrated. Finally, the effect of each reactive state on dissociation is quantified for both nitrogen and oxygen dissociation. The effect of collision partner’s internal energy on simple dissociation is probably negligible, and vibrational energy of the dissociating molecule has the strongest effect. These rigorous statistical analyses enable the development of physics-based models for CFD.