Go on to any car forum, and there’s pages on this.
Supermarket fuels have less additives in there petrol than forecourt, the Ron will stay the same, it’s very noticeable the difference,
With diesel there will be a difference, first it might be the cten number that changes, then which base oil, how it’s fractured etc etc.
But from my experience in a previous life fuel companies keep what they add to fuel very secretive,