i have used both V-power and Tesco 99 in a range of different cars.
In the 172 Tesco 99 is rubbish. I didnt get any extra milage when i did an eco run, and no power gain. With V-power i got about 30 miles more on the eco run, but again, no real power gain.
However, I did have a Seat Leon Cupra before, and the results were different. Tesco 99 gave me less miles, but a big power gain, and a much better exhaust sound - it even popped a few times in low revs :clap:
The V-power gave me more miles again, but less power and sound than the tesco.
In short, Tesco is good if your car has a turbo, and you drive hard like i used to. V-power is good if you want that big extra economy from your car.
Something else you should also remember is that V-Power is packed full of adetives which help keep your engine clean, and in general good condition. They also prolong the life of the petrol should you have it in a car you only drive a couple of times a week. The tesco 99 tends to go off quite quickly.
Basically:
Tesco - Turbo's cars only, use it up and use V-power once a month to flush through.
V-Power - any car, less power but better milage and keeps engine in good nick