Wrong ! The additive required for PU50 , DERV, Super UNL and Super DRV is injected on the loading racks at the oil terminal at the time of loading the tanker .

And I guarantee , that when tankers do deliver to different petrol stations (and believe me when I say its rare as fuck) they have their own specific tanks to deliver into .

For example , I work for Texaco , now the garage we deliver to other than our own sites are Newport Pagnell Services North and South which are Shell branded BUT ! We do not put our fuel in tanks that are labelled Shell only the ones labelled Texaco !