In the past years, the employment of carbon dioxide as an alternative is becoming significant. Its compatibility with synthetic compressor lubricants is still a problem far from a solution. In the literature, only a few data on the Mutual solubility of the carbon dioxide-lubricant systems are present, although it is one of the main properties affecting the selection of the proper lubricant. At our laboratories, a systematic study on the solubility of carbon dioxide in lubricants has been started, trying to identify its dependence on pressure, temperature, and oil chemical structure, In this work, experimental solubility data of carbon dioxide in pentaerythritol tetra-2-methylbutyrate, i.e., a precursor of polyol ester oil, are presented in the temperature range of (243 to 343) K and pressure up to 10 MPa. The experimental data were correlated by means of the Peng-Robinson equation of state with the Huron Vidal mixing rules in which the excess Gibbs energy at infinite pressure was represented by the UNIQUAC equation assuming a temperature dependence of the fitted parameters.