Hi, I have a cupra and do mainly town driving. I have been averaging about 30 mpg on shell standard fuel, Last time I ran the tank to empty and re-fuelled with v power, have driven 200 miles and refilled. It averaged out at 34mpg, I cant say definately that it felt like there was more power, but it is meant to be better for your engine. It also works out that even though you pay more per litre, that you can still gain 1 or 2 mpg. The bottom line is it depends how you drive it I guess. The only true way to work it out is to fill ya tank, do at least 200 miles, refill and see how many litres it takes, times by 4.55 to convert to gallons and divide your milage by the answer. e.g 27 litres to fill up after 200 miles, 27 divided by 4.55, is 5.93 gallons, so 200 miles divided by 5.93 is 33.7 mpg. simples