The newer movies expand the wasteland to three “fortresses” that factions fight for control: the citadel has a fresh water reservoir and food, the bullet farm was a mining town turned into an arms factory, and gastown controls an oil refinery that everyone depends on (and slaves to keep it working). Lore wise, gasoline is one of the commodities they’ve continued creating and exporting.
It very conveniently pumps it’s own oil from the sands! But fiction aside - I do think gas is a resource that would be processed and controlled throughout a mad max like downfall. Too much in war depends on fossil transport to allow that supply chain to crumble. Just reinforces the meme lol.