The compatibility of carbon dioxide with synthetic oils, employed as lubricants for compressors in the refrigeration and air conditioning plants, is a fundamental and still unsolved problem. Mutual solubility with the refrigerant is one of the properties that influences the choice of a particular lubricant for a specific application. A systematic study of the solubility of carbon dioxide in polyolester oils (POE) has been started at our laboratories with the aim to investigate the dependence of this property on various parameters, such as pressure, temperature, and oil chemical structure. In this paper, experimental measurements of solubility of carbon dioxide in pentaerythritol hexanoate (PEC6), which is a precursor of polyol ester based lubricants, are presented in a temperature range of (243 to 343) K and pressures up to about 10 MPa. The uncertainty in the liquid composition measurements was estimated to be from 0.002 (high CO2 molar fraction) to 0.02 (low CO2 molar fraction). 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 pressures was represented by the UNIQUAC equation.