Driving in Europe : some hints and tips...
In France , petrol and diesel are usually quite a bit cheaper at hypermarches
( Carrefour/Auchan/Intermarche/Leclerc etc ) than at "brand" filling stations , particularly the Autoroute-ones ; however , note that the cheap ones usually close the payment-booths by 20.00 , so you'd need a french debit-card , to purchase/self-service in the hours 20.00 to 08.00 next morning ; one known exception is Carrefour Calais Cite Europe , where the manned "caisse" stays open 'till 22.00 !
In Belgium , the speed limit is 120 km/h , the police won't react if you "do" 130 , though ! Fill-up in towns , not on M-ways : "Jet" is normally cheapest!
Driving southerly from Aachen , Germany , the first big rest-station ,"Aachener Land Sued" has some truly great German specialty hot and cold foods , at v. reasonable prices , in superbly-neat self-service resto = always Recommended!
But , as far as I know , the cheapest fuel of all is in Luxembourg.Once you're there , make sure that you get to spend a day , at least , in fabulous, well-preserved Trier , on of Germany's oldest towns...