Petroleum along with Oil Sands and other items is a way to create Diesel Fuel. Diesel Fuel is used to fuel Diesel Locomotives and Diesel Engines. These ores can be found between layers 58 and 70, and spawns only beneath the surface.
 The ores are set to spawn with the default setting, but if one wants to prevent them from spawning, the option ENABLE_ORE_SPAWN in the "Traincraft.cfg" file in the "config" has to be set to false.
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