What about your own X5's though?

Half the time I put in the UK's regular cheap stuff (95 RON) and the other half I try to find somewhere that sells Shell V-Power (previously aka Optimax) which is rated 99 RON.

Tending to go more for the V-Power at the moment since I doubt the previous owner bothered and it's meant to help clean the engine (2002 X5 4.4).

How many people can say they notice the difference in which fuel they have in their tank on these cars?