Heavy oil is a liquid produced by refining crude oil in an oil refinery or extracted on Fulgora using an offshore pump. It can be processed into light oil, solid fuel and lubricant. It is more efficient to process heavy oil into light oil before creating solid fuel from it. It can also be used as ammo in flamethrower turrets.
Heavy oil can be obtained on Vulcanus using simple coal liquefaction. This can be upgraded to coal liquefaction once some initial heavy oil has been obtained.
