They do Alexx, on Saturdays and Sundays there is a steady procession of trucks, without trailers, crossing solely for the purpose of buying fuel. The ferry companies and the train offer special deals on tickets for this purpose I believe.
Many would also take the opportunity to stock up on beer, wine, tobacco products and maybe even hit one of the supermarkets for food products as well. Large boxes of washing powder and dishwasher tablets are another popular purchase.