Heavy fuel oil (HFO) obtained from crude oil distillation is a widely used fuel in marine engines and power generation technologies. In the present study, the combustion characteristics and performance of heavy oil are investigated. Further research on heavy oil is developed by adding content of Liquefaction Bio-Oil, because of its complex nature. So as to better understanding of HFBO combustion process and to improve efficiency and control emissions. The techniques used to study the heavy oil is TGA-FTIR, Single droplet, Gas analyzer and Spray combustor. All the required techniques are used to investigate heavy fuel blended oil (Mixture of heavy oil and Liquefaction Bio-Oil) combustion behavior with various HBFO of 3%, 5%, 7% and 10%. The combustion behavior of heavy fuel blended oil was performed using the thermo-gravimetric analysis (TGA) at temperature 30 °C to 800 °C at various heating rates of 5°C/min and 10°C/min in air atmosphere. TG and DTG were used to study the mass loss characteristics due to the thermal degradation of HFBO. Single droplet and spray combustion experiments of heavy fuel oil with Liquefaction Bio-Oil are used to investigate the evaporation, atomization, combustion behavior and improve efficiency. The results show that improve in the combustion performance and characteristics of heavy fuel blended oil by using TGA. The droplet test results are good agreement with HFO and heavy fuel blended oil (HFBO) in two cases, found that ignition temperature, burnout temperature and combustion index are more satisfactory.