Unlock the Refining Forge engram
Gather Hide, Wood, and Flint
Craft a Refining Forge
Place the Refining Forge and fuel it with Wood or thatch
Put Oil and Hide into the Refining Forge
Wait for Gasoline to be produced
Use Gasoline to power generators and other industrial structures
Get Oil from underwater nodes, trilobites, basilosaurus, dunkleosteus, or oil-rich areas
Get Hide by harvesting animals with weapons or tames