The gas solubility of pure oxygen and of pure carbon dioxide as well as of their gaseous mixture are measured in the ternary liquid mixture cyclohexane + cyclohexanone + cyclohexanol at 313.6 K with a high-pressure view-cell technique using the synthetic method. The new experimental data are used to assess the capability of molecular simulation and conductor-like screening model (COSMO)-SAC to predict multicomponent fluid-phase coexistence behavior. These methods are also compared systematically on the basis of experimental binary fluid-phase coexistence data. In that comparison also the Peng-Robinson (PR) equation of state is included as a reference. Molecular simulation and COSMO-SAC yield good results and are found to be far superior to the PR equation of state both in predictive and in adjusted mode.