fuel As a command 12 categories below fuel Narrow by material 5 chemical 4 compound 3 coal 2 body-part 1 carbon 1 chemical-element 1 commodity 1 oil 1 physical-object 1 tissue 1 wood 1 coal 2brown-coalbutanecharcoalcokefirewoodfuel-oilgasolinehard-coalkerosenenatural-gaspropane