Miscible carbon dioxide flooding is an effective method for Enhanced.Oil Recovery (EOR). The main objectives of this study are to investigate the influences of mobile oil saturation at the start of CO2 flooding and reservoir oil viscosity on oil recovery by CO2 miscible flooding. Actual fluid and rock samples used were obtained from a field under development in the U. A. E To achieve the objectives of this study, six core-flooding experiments, were performed using supercritical CO2 slug size equivalent to 0.15 hydrocarbon pore volume (HCPV-). under simulated reservoir conditions of pressure and temperature. Five experiments were performed under different mobile oil saturations in the range of 32.74 % (i.e. after complete water flooding) to 79.43 % (with no water flooding). The sixth run was applied using heavier crude oil viscosity. All flooding experiments were carried out using actual core samples extracted from the field and flooded using actual reservoir fluids. The;'results indicated that the earlier the start of CO 2 miscible flooding the higher the oil recovery. The start of, CO2 flooding with the core saturated with oil at irreducible water saturation produced 98.61 % IOIP while flooding with CO2 after complete water flooding recovered 83.31 % IOIP. Furthermore, the increase of oil viscosity decreased the oil recovery by CO2 flooding The injection of the same CO2 slug size produced 98.61 % IOIP for oil viscosity of 1,03 cp while the same application recovered only 86.11 % IOIP for heavier oil viscosity of 2.62 cp. The main conclusion drawn from this study is that while the application of CO2 flooding has successfully recovered more oil either after water flooding or as a secondary process, the application at initial oil saturation recovered the maximum oil recovery.