Phase behavior was observed for the systems bio-oil + diesel + carbon dioxide and bio-oil + tail water + carbon dioxide at temperatures from 353.15 K to 423.15 K and within the pressure range from 0.1 MPa to 49.0 MPa. First, equilibria was observed at ambient pressure and temperatures of 353.15 K, 383.15 K, and 423.15 K in a glass flask, which was heated by an electric heater. Afterward the equilibria was observed under elevated pressures in an optical cell (up to 49.0 MPa) and temperatures of 353.15 K, 383.15 K, and 423.15 K. It was discovered that the system bio-oil + diesel + carbon dioxide is immiscible under ambient pressure and temperatures of 353.15 K, 383.15 and 423.15 K. The complete miscibility of bio-oil and diesel in the presence of CO2 could be at temperature 353.15 K detected at pressures above 49.0 MPa, while at temperature of 383.15 K the transition from a dual liquid to a single liquid system was detected at 27.0 MPa. It could be concluded that the miscibility of bio-oil + diesel system in the presence of CO2 depends highly on pressure. Additionally, data on solubility of carbon dioxide in tail water and solubility of carbon dioxide in diesel fuel are presented.