The solubility of carbon dioxide, CO(2), in dipentaerythritol hexaheptanoate (DiPEC7) and a polypropylene glycol dimethyl ether (PAG1) was measured at 283.15 K, 298.15 K, 323.15 K, and 348.15 K, and pressures up to 7 MPa in a high-pressure gas solubility apparatus. A total of 42 pTx values were measured with an isochoric technique, having a mole fraction relative uncertainty of 4%. The results for DiPEC7 together with the experimental literature data show that, in the present analyzed range, the CO(2) solubility expressed in mole fraction in the polyolester oils increases with the number of the polar carboxyl groups. In mass fraction, the solubilities of CO(2) in DiPEC7 are lower than in PAG1 and also lower than in several other pentaerythritol esters (PEs).