Just across the smaller of the two ponds, in the Netherlands, 1 litre of petrol costs 1.49 euro. A gallon is 3.78 liters, that makes it 5.63 euro/gallon - crunch, crunch - that's very close to the UK price in dollars.
Of course that includes all kinds of taxes plus VAT, but that pays for a lot of those public welfare institutions and conveniences that you won't find in the US.