>>76314860By the time the bombs dropped, there were still gasoline cars (though almost all of it was reserved for military/military-industrial use with rationing brutal in the US). The US was the only country this was definitely true for except maybe Mexico and Canada (it was never made clear if their own dwindling reserves had been emptied). The US also had recourse to microfusion technology, though it was new and expensive in civilian use and production was bottlenecked heavily.
China and Europe were both out of oil. The former ran out not long after their disastrous invasion of Alaska, and the latter ran out after getting into a nuclear war with the dirkas years before that.
Besides a very small amount of oil-based fuels left to the survivors, it's also likely that they're burning ethanol. And the microfusion stuff still works if you can slap together a working vehicle. The realistic bottleneck is probably going to be all the rubber. Not just tires, but all kinds of gaskets.