You make a very good point. I've noticed the same phenomenon. I'm sure that most motorists have a preference for a certain make of petrol in the same way as for other commodities. They really believe that one gives better performance than another. This might be true in some cases but I discovered many years ago that they very often come from the same supplier, even the same petrol tanker.
I always buy my petrol from the likes of Texaco or, Shell NEVER from the supermarkets!!!!
Why? most supermarket fuels are cheaper than Texaco et al, but, they scrimp on things like detergents in fuel (that help to keep your fuel lines clear...) not to mention sometimes suspect octane ratings.
I'll try to find a link with some more information.
For what its worth, my 2.8 engined BMW is much more responsive on high octane fuels, such as Shell Optimax, expensive but noticably better.
My truck gets the cheapest Diesel fuel my employers can locate all other factors are secondary to price...... ::)
I'd love to pay some of the prices quoted here guys! I have an 85 Litre fuel tank..... :(
Posting drivel here since Jan 31st, 2002. - That long!
"He who laughs last, thinks slowest."