Here we go again . . .
We will always have 2 different camps here. Those who are convinced that supermarket fuel is inferior and those that think it's all the same.
But let's try to go off real-world experience.
Here's mine after driving Alfa diesels for about the last 8 or 9 years and often dipping into the world of "I wonder if this fuel is better than that fuel?" I think I've tried them all, including the BP Super stuff and Shell V-Power (for extended periods) and I've come to this conclusion (which I know is my experience alone and NOT gospel):
Stick to Shell regular diesel.
Avoid supermarket diesel unless absolutely necessary.
BP is better than supermarket but not as good as Shell.
Shell V-Power makes no discernable difference to power or mpg (again, in my opinion).
I've never tried Total.
Sucumbing to temptation and using the 15p off voucher from Morrisons last week has only reinforced my belief that the car runs smoother and feels a bit more nimbler on the Shell stuff.
Also, I don't know that this is related, but my brother insists on using ONLY supermarket fuel in his 2005 GT 1.9 JTD and so far, over the last 18 months, we've changed his MAF, EGR and just last week cleaned his MAP sensor (but I think it needs replacing) but he is still getting the dash-warning light coming on at regular intervals.
So far (fingers crossed) I've not had any of those problems in almost 20,000 miles (to be fair, the EGR valve had been changed the day I picked her up).
Coincidence? Maybe. But when I look at the couple of quid I could have saved going to Sainsbury's I really don't think it's worth it.
As for using additives. Why? Just put decent stuff in that will keep things clean anyway. I think it's a false economy.
Like I said, just MHO.
Oh yea, I joned the Shell Drivers Club and every few months I get a £5 off voucher which is nice. I don't work for Shell BTW!