£1.30 a litre for the 95 octane stuff usually 12 pence more for the 97 octane.

for the OP the 4.6is is a great car to drive, I have owned mine for the last 3 years only problems that I have had have been the suspension mounting bushes, can probably class that as wear and tear, but well worth having a close look at them. Also check this buyers guide

E53 X5 buyers guide faq