Fuel Does It Matter Which!

biggriffin:
Go on to any car forum, and there’s pages on this.

Supermarket fuels have less additives in there petrol than forecourt, the Ron will stay the same, it’s very noticeable the difference,

With diesel there will be a difference, first it might be the cten number that changes, then which base oil, how it’s fractured etc etc.

But from my experience in a previous life fuel companies keep what they add to fuel very secretive,

I think youll find the difference is only apparent on SOME vehicles? Some more advanced engines will alter the timing according to the fuel type used. Some others will not be able to (within the parameters set at the factory) be able to take advantage of any "superior" fuel. As you say the fuels bought by supermarkets may have different, or fewer, additives, but surely they all come out of the same refineries as "branded" fuels? And testing for fuel economy in the real world is difficult. What youre trying to measure is less than the normal variations. Its not impossible to do, but involves a lot more than doing a couple of fill ups at the pump. Add in biased (intentional or innocent) reporting, and human interpretation of results, as well as the financial incentives for some and its a minefield to find the truth.