my car isn't mapped ... yet
i did a few weeks of testing some years ago
i spent the same amount of money on fuel (vmax and non) and got similar mileages over similar trips to and from work. i did this a few times each so it wasn't the after effects of either fuel. i concluded the more expensive stuff was worth it but i've also heard but dont quote me (not sure if it was something i read or a TG review) that the additives in vamx "help" the engine last longer and run better????
anyway i'm sticking with vmax on the fact the "extra cost" is not actually any extra because it gets more miles ... so being fairly similar in terms of value and
... more importantly 20 quid extra per month is pennies esp when you compare a night out you woulndt bat an eyelid at paying for a round of drinks ... lol