Kiltox:
Define premium fuel?
If you mean standard 95 octane from BP and are saying it's fine compared with 95 octane from Tesco there's something terribly wrong with your car - it's the same fuel in most cases.
If you mean "super" unleaded - use Tesco 99 RON because it's the best of all of the super unleaded fuels as proved time and time again.
Which car ?
Standard 95 Octane
It's A Fiat Multipla
Had a problem where on the display it said "Engine CTRL - Contact Garage"
Had it diagnosed and it was a Cat and Lamba sensor malfunction, After mechanic reset the ECU it was fine.
I was advised from the mechanic to avoid Supermarket fuel stick to premium petrol, Theirs been several people with similar issues, Especially over the last couple of years.
He's 99% certain that it was the petrol that caused the fault codes and if I use premium petrol it shouldn't return.
I've followed his advice and 6000 miles on it's been fine with no problems.
Contrary to popular belief their is a difference between "some" supermarket fuel and premium brands, They have additives in the fuel.
The supermarket prior to the fault I used was a Sainsburys petrol station.
It might just of been a bad batch of fuel but not worth having the problem return.