Eric - 06.07.2019
Filling up with LPG at a motorway filling station is stealing money from your own pocket! Prices on the motorway are about €0,25 higher than other stations selling LPG around Rotterdam.

You can take this exit 22 (Alblasserdam/Papendrecht West) and turn left towards Papendrecht. You will find a Total filling station selling LPG on your left hand side, only 300 metres from the motorway. I think it closes around 21h in the evening, if I remember that right.

The closest Shell selling LPG at much lower prices would be on Dierensteinweg in Barendrecht. It is right beside exit 20 (Rotterdam IJsselmonde), south of A15 and it's open non-stop, so there is no need to steal money from your own pocket! ;-)

Eric - 21.02.2020
Today I was driving towards Rotterdam on A15 motorway. Out of curiosity I stopped by here and was very surprised to find Shell's LPG-pump indicating a price of €0,659 per litre of LPG. This was around 20h/8hPM, when the Total filling station just off the motorway is still open. I did not buy LPG here myself.

Earlier this same evening I have heard that Shell now changes their prices up to 10 times per day, depending on how fierce competition is in the surrounding area. As soon as other filling stations close, Shell-employees are instructed to demand a higher price for LPG. This is why I did not update the price of €0,879 per litre of LPG, which would be a normal price for buying LPG on a motorway in the Netherlands. I had forgotten that fuel prices vary between day and night.