Feasible from Canada although Mexican toll road prices would probably eat up all your savings.....
Spar @ Portglenone: 175.5p/litre
Crawfords (Carrickanielt Rd in Maghera - 5 minutes off the A6): 177.7p/litre
Russells @top of Gilnahirk Rd: 189.9p/litre
Tesco @Knocknagoney 193.9p/litre (Sainsbury's Holywood 192.9p/litre)
Looks like the supermarkets have decided to stop using fuel as a loss-leader as Asda in Newtownards isn't very cheap anymore either.