i remember a long as hell post either on here or another ford forum a while back, discussing the virtues of each fuel supplier

and im sure esso/texaco/total chain fuel suppliers did the best quality 'cleanest' super unleaded

and the shell v-power/optimax suffers from its octane dropping off at a considerable rate in comparison, due to it being re-engineered to its high octane state rather than just octane boosted

personally though wen it comes to filling up the RS with fuel, i will just go to shell, as its the most local place lol