I suspect both sides are correct here.......all petrol comes from the same amalgamated sources, but after it leaves the major bunker sites it does get additives stuck in it.........
There have been various well documented differences in the stuff that comes out at the pumps.....a few years ago I believe it was Safeways who had some problems with gumming injectors from their lead-free petrol........and as several people have noted, different cars do perform differently on different fuels....When i had a bunker card I'd always go to a BP 'cos the Rover 420 i had at the time felt noticeably quicker on the stuff......
At the end of the day though, all the fuels will do what it sayson the can......some might be better than others in certain engines, others worse.
(PS Greg, as a student I worked in various food factories.....Heald's Orange Juice factory in Maidstone (now defunct) used to supply both Tescos and M&S......both products originated from the same concentrate drums...the only difference was the concentrate v water ratio.......I packed the same meat pies for Asdas as I did for Sainsbury's, and there was ZERO difference between Waitrose milk and Lidl milk apart from the design of the tetrapak..........the only serious difference was in fruit and veg.....i picked strawbs in Kent and there were three grades....jams, normals, and M&S.......we got paid different amounts for each crate of punets of each different sort and there were some major size/quality tests for a punnet to be declared 'M&S passed')
Ahhh those were the days..........work all day, get 12 quid for it, put three in the Mk1 escort tank to get to the fields the next day and piss the other 9 up the wall of the Stone Horse in Wainscott that night
