5th gear carried out a test on quite a few fuel suppliers years ago, Asda came out bottom of the pile.
I acknowledge that your average person driving an average car probably won't notice the difference, but I would rather put a quality fuel in my car, it makes no sense to me to put the worst option available in my car just to save a few pence.
If it’s a high performance petrol I agree, you’ll see the benefit going for super over boggo supermarket 95 and agree for your average runabout, it’ll be fine.