Bunker fuel is a type of fuel used primarily in ships and large vessels. It is a thick, heavy oil that is derived from crude oil and is specifically designed for marine engines. Bunker fuel is essential for powering ships across oceans and is stored in large tanks on board. Due to its high viscosity, bunker fuel requires heating before it can be pumped into engines. It is categorized into different grades, with IFO 380 and MGO being the most common. The use of bunker fuel has raised environmental concerns, leading to regulations aimed at reducing emissions from ships.