Mmm, I (just) old enough to remember when the £1 gallon loomed large and threatening on the horizon. The world as we know it didn't end then, and I don't think it will end this time. However I can see a time when this sort of price increase or more likely a sudden problem with petrol supply will, maybe not cause the end of civilisation as we know it, but could cause an interruption to it.
Recall the fuel protests of 2000 or 2001 (I'm not sure which year it was!), these didn't go on long enough for any real lasting damage to have been done. If they had gone on for maybe just a few more days, a the super markets started to run low on food, imagine what would happen. It's said we are all three meals from barbarism.
I can't see this sort protest lasting for long if the food did start running out, but what if there was simply no way to get new supplies of fuel? A large scale war in the Gulf could do this, what then?
I don't think civilisation would collapse, lots of very powerful people have vested interests in keeping our sort of civilisation running, but I just a few days of of the sort of chaos that could happen, would cause huge damage to society.
However with me being a pessimist, it think it would take something like this to shake us out of the madness where of car and road building we are currently in.
...Oh I seem to have have got on my hobby horse a bit and wondered off topic, never mind!