This paper investigates the extent to which alcohol-treated carbon dioxide (CO₂), a mixture of alcohol and CO₂ equilibrated at experimental pressure and temperature, can lead to greater interfacial tension reduction and greater oil swelling than can pure CO₂. Experimental measurements of interfacial tension and swelling behavior are made using a high-pressure, high-temperature visual cell at 70 °C. Two sets of fluid pairs are used: pure CO₂ and oil, and alcohol-treated CO₂ and oil. Two types of oil are used: a mixture of 35% hexane and 65% decane (C ${}_6$-C ${}_{10}$ mixture), and pure decane (pure C ${}_{10}$). Ethanol and methanol are used to prepare alcohol-treated CO₂. Numerical simulations are used to estimate a reduction in the minimum miscibility pressure when using alcohol-treated CO₂. Interfacial tension between alcohol-treated CO₂ and oil is found to be 0.02 to 2.2 mN/m less than that between pure CO₂ and oil. Simulation results suggest that alcohol-treated CO₂ yields 0.2 to 1.2 MPa lower minimum miscibility pressure compared to pure CO₂. Alcohol-treated CO₂ also is found to cause 6% to 43% more swelling of oil than does pure CO₂. Interfacial tension and swelling results suggest that alcohol-treated CO₂ yields better miscibility with oil compared to pure CO₂.