True, but I'd expect them to last longer than gasoline, yet that's something some post-apocalyptic hellscapes seem to have plenty of.

It depends how fast the planet depopulated. In Mad Max the original problem was water shortages. If most of the population was wiped out in the water wars, it’s reasonable that the dregs of fuel in the system could last the few survivors a long time.

In case of dragons there might also be helicopters around.

I guess the idea that cars would be around after the apocalypse comes from the diesel engine, which can basically run on vegetable oil.

You can make tires quite easily with simple tools.

You can't make gasoline as easily - or extract oil.

No, you can't. Not puncture-resistant, durable, pneumatic tires that don't have to be changed every mile.

Not tires that don't turn into chewing gum in hot weather, or under hard braking, and don't freeze and crack in cold weather.

Ethanol?

Is it more efficient (and/or easier) to make ethanol to fuel an internal combustion engine, or instead to burn the fuel you would have used to distil the ethanol to fuel an external combustion engine? (i.e. a steam engine.)

Ethanol wins. You can use ethanol to make more ethanol. Its a positive yield. Has been for years.