As an experiment I have been following a few guidelines with my last tank of RON95 petrol:

I managed to travel (mainly rush hour commuting up the M3/M25) 426.9 miles on one tank of fuel taking 56.95 litres to refill it to the same point. This equates to 7.496 miles per litre; 34.077 miles per UK gallon; 28.372 miles per US gallon.. The fuel warning light came on at 370.3 miles.

Needless to say, I'm pretty impressed with the economy I achieved.

I will repeat the experiment with RON98 next month to see if it make a difference, and justifies the extra 7p per litre.

I would be interested to hear if anyone has travelled further than 426.9 miles between refills.