It all depends where you gas-up so to say. I payed 1.52 euro/liter for UL95 at a shell station in Hasselt. Around Spa, all stations marked up the prices, cause they get away with it. Diesel is 1.31 at the same pump I get my petrol. A little bit more then in France, but a lot less then in Holland!
And yes, Andy is right, Total in belgium, only sell the premium petrol and diesel, at least at all the stations I have been so far.