The Fuel that Burns Well (よく燃える燃料, Yoku Moeru Nenryou, lit. Well-Burning Fuel) is an event in Tomba! 2: The Evil Swine Return.
Talk to the miner in the north-west part of Coal-Mining Town who is shoveling coal onto the conveyor belts to active the event.
Go to Pipe Area and climb down the long chain near the entrance to Waterfall of the Heavens, the very same that reveals the treasure chest containing the Ice Boomerang. A red treasure chest can be found to the left, hanging from a short chain. Open the chest, collect the Power Coal inside and head back to the miner.
Once back, talk to him and the event is cleared after a short cutscene.