I've seen you recommend V-Power fuel multiple times and seen the reasons why - but I've always been told that if a car is regularly run on a lower grade of fuel (for example always supermarket fuel) then the car adapts to get the best out of that type of fuel, and should the owner then switch to better quality fuel, the benefits will not be felt as much as if the car has always been run on quality fuel.

I have a 194,000 mile, 13 year-old Fabia SDI that I believe was previously a taxi (which would explain the high mileage) and I usually put the cheapest fuel I can find in it, as I can't believe a taxi driver would bother with premium fuel - so if the above is true, there'd be no point in spending the extra money for the better fuel.

If I were to opt for premium fuels when available, would there be a noticeable difference in economy and performance with a car this old, or would I be wasting my pennies?