Bunker oil is a dense, heavy fuel oil used primarily as fuel in ship engines. It is obtained through oil refining and comes in various grades based on viscosity and sulfur content. Key grades are IFO 180 and IFO 380. Bunker oil is regulated, particularly on sulfur content, to reduce pollution. While it provides energy, bunker oil also has environmental impacts like air pollution and greenhouse gas emissions. Due to its properties, bunker oil requires specialized storage, heating, and handling. Its price fluctuates along with crude oil and other market forces. Recently there has been a focus on cleaner alternative fuels and technologies for ships to reduce bunker oil's environmental effects.