I was being cynical with that remark about a whip-round but the thread has gone off at a tangent somewhat since then.
In case anyone is still unclear about the quality of supermarket fuel compared to that sold in the premium brand stations, you can research the subject on the internet as I did a couple of years ago. When you have spent hours trying to discover the answer, you will eventually find the important stuff which, without trying to be technical as I'm no scientist, concerns the additives that the big companies put into their fuels.
You may have heard tales like, "It all comes out of the same tanks at the depot."....or "My mate's a tanker driver and he says...." Well, the truth is that the fuels delivered to supermarkets is fairly basic stuff whereas that which is sold by the likes of Shell, BP, Texaco et al is better on account of the additives used. Evidently, lab tests have demonstrated that there is truth in those claims about extra mileage with certain brands but those fuels come at extra cost so there is some arithmetic involved if you really want to determine which is better value.
For what it's worth, my own car always gives me a few more miles on Shell regular diesel than on Tesco's stuff. That is a fact. The car always seems livelier also on Shell but that may be a psychological thing on my part and not fact; I really don't know. In any event, I have no qualms about using supermarket fuel and it certainly isn't **** although I understand someone using that term in the same way as someone saying, "Arsenal are brilliant and Spurs are...." It's a relative thing.
Now what was the subject of this thread....?
Indalo
ps I'm not going to research it all again but cetane improvers were involved amongst other things.