Mine black rocks in the snow biome, deep ocean, or oil-rich caves with a pickaxe or metal tool
Kill Trilobites, Leeches, Basilosaurus, and other oil-dropping creatures
Tame and harvest an Ankylosaurus for better oil collection from nodes
Build an Oil Pump on top of an oil vein in the ground
Harvest underwater oil nodes with a pickaxe, Ankylosaurus, or Dunkleosteus
Use a Phoenix or other map-specific methods where available
Craft oil from certain creatures or resources on maps that allow alternative oil sources
Loot oil from supply drops, caves, and certain mission rewards
Use a chainsaw or advanced harvesting tool on oil-bearing creatures when applicable