Can't disagree with you but just can't get myself to splash out on the good stuff .
I'm not being arsey here but I'd love to see some evidence on this. Does anyone have any?? If you're right then I agree and I should stick the better stuff in. As far as I'm aware the difference has always been in people's heads as opposed to any factual evidence.
That said, whilst I didn't really notice when I changed from 95 to 98 (back in the day ) but do seem to remember when I dropped back from 98 to 95. But, again, was it all in my head .
Nothing very Scientific but last November I drove down to Essex, filled up with Shell V Power before i set off and reset the trip, filled up again with ordinary Shell unleaded on the return and reset the trip, on the exact same return journey I showed 1mpg less thats approx 4% worse, about 6p per gallon. Not very scientific but good enough for me to stick to the V Power.