I used to use Sainsburys Super U/L in my 2013 GTI PP (which was tuned from the factory to run on 95). It always ran fine and being a busy fuel station the petrol was always fresh.
I’ve seen some massive hissy fits in fuel threads over the years so I’m keeping away from discussing ‘Internet facts’ here but in 30 years of driving I can say that all of the (very) numerous cars I’ve owned which have been standard and modified tend to feel different on different days.
Some mornings I’ll get in and the engine feels about as willing as a donkey in a bad mood and other mornings the car feels like it’s straining at the leash like a puppy. And everything in between.
I’ve long since concluded that rather than what sort of hormonal imbalance the car might be suffering from it is indeed as much down to atmospheric conditions

Avoiding the sciency stuff as I’m thick as pig crap it has to be said that after running my Ed40 exclusively on Tesco Blue Stripe 99RON for two and a half years I pulled up to find the 24h fuel station closed overnight for ‘technical’ reasons, so I had to swallow hard and spend 8p a litre more on Shell V-Power.
I’d always been incredibly sceptical about fuel differences but have to eat my words here as there was no doubting that it definitely felt like a bit of cracked pepper had been sprinkled on the car’s mashed potato as it quantifiably felt slightly perkier running on Shell.
You might take it from that little snippet that I’ve been converted but alas I’m back running Tesco 99 in the TCR due partly to licking my considerable financial wounds and the fact the DSG feels so curious in its programming at times it would take rocket fuel to make a noticeable difference.
On a nicer note, whoever bought my CS had around £60 of V-Power as a bonus. Merry Xmas.