i also always run mine on shell V-power just because i feel its a higher quality fuel and i watched fifth gear once where they compared premium to supermarket... have a watch yourself :-
http://www.youtube.com/watch?v=ezjknhwcQXU
as you will notice the power difference is the biggest i think and this increases with the more power you have for example i would imagine a high powered turbocharged car would see a massive difference, Cupra R, Evo's, subaru's etc. A remapped PD170 would have considerable improvements, and i don't know whether you drive your car like you stole it but i wouldn't class 40mpg as good on any fuel... I'm currently getting around 50+
http://www.youtube.com/watch?v=ezjknhwcQXU
as you will notice the power difference is the biggest i think and this increases with the more power you have for example i would imagine a high powered turbocharged car would see a massive difference, Cupra R, Evo's, subaru's etc. A remapped PD170 would have considerable improvements, and i don't know whether you drive your car like you stole it but i wouldn't class 40mpg as good on any fuel... I'm currently getting around 50+
