I know its not Europe but my running mate did 27yrs with the main fuel hauler in western Canada and a couple o yr after retiring with a smaller company…well I asked him why he never fueled up at a certain retail companies locations and he told me …"every yr the refinery he ran out of shut down /cleaned out so many storage vessels in the winter (think -20c ish) and this certain retail company would buy the contents sometimes diesel/petrol/avgas and my mates company would come in mob handed and empty the vessels out and take to whatever locations they were told. He told me it was a miserable job as the petrol/diesel/avgas had so much condensation in it froze in the pipes when pumping out. Can only take this at face value as he is not known for telling tall tales. This retail company fuel is always a couple o cents cheaper than everyone else.