The significance of petrol is one of the things covered in the "Crash Course" linked from the Time to quit bailing thread.

Put a gallon into your car, drive until it runs out, then push the car back home again. That'll give you an idea of how much human labour it is worth, and what life will be like when it's gone. It's not running out, exactly, but it's becoming asymptotically rare and when the time comes it will become unavailable quite rapidly.

I dare say the people panicking don't have a deep economic grasp; nevertheless the occasional shortage is like an intimation of mortality for someone who thought they would live forever.