Baz, You're right about all the various companies loading from the same depots, but the major "brand names" have an automated system that injects their own particular additive into the base product as it is being loaded so ordinary petrol/diesel becomes their "own brand" petrol/diesel. I've always found I get at least 25 miles more from a full tank if I've filled up at a major oil company site as opposed to a supermarket or non branded smaller retailer. John.