petrol prices per gallon in Ireland
Northern Ireland has (I think) the same prices as UK, but they may have a rebate because Eire has cheaper fuel and the border is fairly open.
http://www.see-search.com/business/fuelandpetrolpriceseurope.htm has a list of European prices as of 27th May. The prices obviously depend on currency fluctuations as well. To get the price in US dollars per US gallon, multiply the pence per litre by 5.3 and divide by 100 (3.8 litres per US gallon * 1.4 dollars per pound).
Eire has a price (Unleaded) of 58.4 = 3.10 US dollars per US Gallon.
Of course as everbody knows, Irish miles are longer or does it just seem that way?

Rod