As of today (11th March 2022) The average price for unleaded fuel = £1.55 per litre
There are 3.8 litres to 1 US Gallon - that would cost £5.89 per gallon
The exchange rate is $1.30 = £1.00 .... So a quick bit of math(s)
The equivalent price would be $7.65 per US Gallon
Now that's what I call .... Expensive