I use Tesco 99 over shell, main reasons being my local fuelstop is tesco, i get my clubcard points, but comparing the 2, i get identical performance, mpg when ive used both types of fuel when ive been nearer a shell stop.
My nearest shell garages have had credit card fraud on a number of occasions, and i try and refuse to go there using my debit card.
I dont trust them with my card.Im not mentioning Nationality.
Sorry, thats just my experiance.