Ever see a post-apocalyptic film where people are driving cars years after the fall of civilisation? Sorry, car fuel doesn’t work like that.
This is one of my pet peeves with films set after the fall of civilisation: people driving cars. In The Quiet Earth, a film written by my former university lecturer, the protagonist (who is seemingly stranded alone in an abandoned planet) likes to take random cars and drive them around. The Walking Dead has people still driving cars ten years after the zombie uprising. Alas, this is impossible.
Modern car fuel is a blend of many different compounds: in addition to gasoline, it can include ethanol, tetraethyllead (a replacement for lead compounds), antioxidants… all kinds of goodies. Because it’s a blend, fuel that sits in a tank too long will separate and become increasingly useless.
Fuel doesn’t just suddenly stop working, of course. As it separates, it’s just more likely to gum up the internal workings of your car, until eventually it won’t work at all.
Okay, so how about diesel fuel? Well diesel is even worse. If even a little water gets into diesel fuel it can develop a condition usually called “diesel bug” – in reality, this is the growth of bacteria or fungi on the walls of the tank or surface of the fuel. If your diesel fuel is older than a year, there’s a good chance your car is going nowhere.
The Generalist Academy 
It’s hard to find post-apocalyptic worlds based on bicycles. The wonderful “Six String Samurai”, set in 1950s America post-apocalypse (Elvis has just died, and America needs a new king) is one. There’s an amazing scene of our hero pushing his bike through the Devil’s Golf Course in Death Valley.