Well it's here!...SUMMER DIESEL at last....

I've seen a few posts that suggest that the brand of fuel can make a difference. I'd heard this before but never paid much attention. I tend to fill up at Sainsbury's for the nectar points (pays for booze at Christmas), but am I likely to get a better quality of fuel at the (slightly nearer) BP, Shell, or ESSO garages?

Not too bothered about the petrol I'm putting in my Astra, but thinking ahead to the diesel I'll be putting in my GL2 when it turns up...