Yes it's difficult because there's nobody on any car forum who has extensive breadth and depth in the subject of oil fields and refineries, so as to be able to say if/why e.g. Shell petrol is better than e.g. Tesco petrol (or not). Although the petrol at both forecourts will meet EN 228 (?) the specs e.g.1 and e.g.2 contain min and max values that, in the mix, may have different effects (and that's before additives are put in).Big Col wrote: ↑Thu Oct 22, 2020 8:34 pm Brians point about crude is interesting. In my college days a small amount of lecture time was spent on lubrication. My understanding was that the refining process cooked the crude and different products were drawn off at different levels. Tars and the like at the bottom and gases at the top with spirits and liquids at various points in between. The quality of the input determined the ease and costs of refining rather than the output. The output generally being highly monitored for quality. The lighter stuff from the North Sea is said to be good for petrol and gas production.
Although Shell no longer have any refineries in the UK , Shell fuels come from refineries on the continent into various pipelines and storage depots in the UK. So it's probably still true to say that what you get at a Shell forecourt comes from a Shell facility at a general storage depot, the product having come from a Shell refinery on the continent, and the crude having originated from an oilfield in which Shell have an interest. The point is that e.g. Shell fuel has a clearer provenance than e.g. Tesco, but that doesn't necessarily mean it's worth paying more money for it. Their claims also tend to be on the additives they use rather than provenance.
As an example of a storage depot facility, this image shows the various operators at Buncefield in 2005 at the time of the fire there.
But with a lot of brands disappearing it's anecdotally becoming less clear as to what part of the storage facility supplies each supermarket.