There is a filling station right at the Mauritania border, and a big new station about 200km between the border and Nouakchott with a shop and ice creams. Oh ya this border open between 9am and 5pm.

We were with someone at that station who was flashing his "wad" in front of everyone. We got charged 2.50 euros per coffee as a result! They are a miserable bunch in there. Just buy fuel!!

We all have different experiences.
Roger, just to give an alternative view to yours, we passed through there in early Feb and camped on the sand at the back on the fuel stop.
We'd no problems and thought that the Malian guy who was running the petrol station was one of jolliest people we met on whole the trip.

We also changed Euros for Ougiyas in the petrol station for the correct exchange rate.
You can also pay for the fuel with Euros if needed.

We went into Nouadhibou. It's about 30kms out of the way onto the peninsula but we filled there before heading south.

There is a fuel station about 50kms south of the junction for Nouadhibou/Nouakchott/Border.
They had petrol but would only sell in 10l quantities.

I stopped at this station halfway to Nouakchott in January and we all filled up. On my way back, alone in February, I calculated that I could just reach here on one tank full (41ltres) after leaving Zebrabar in morning. Rolled in on fumes just to be told they had run out of fuel and I'd have to wait over 24 hours for next delivery. Station owner could not have been more helpful or friendly. He offered to get his brother to drive down from Nouadibou with a 20lt can if needed or I could stay overnight at station. I thought there was no point waiting for his brother as it would be dark by then and I didn't fancy that route after dark so made myself comfortable.

The station owner and staff in cafe were excellent and provided me with fish and chips, ice cold fanta and coffee. After a couple of hours, a shady looking character stuck his head around the cafe door and asked if I was the biker out of fuel. He explained that he had a spare 30 litres in two cans in back of his toyota pickup and would I like it?

Within seconds I had bike refueled and knew I could still make border before nightfall. I asked him how much I owed him for the fuel expecting an eye-watering price. Instead he looked offended and told me he would not take any money as it was his Islamic duty to help someone in the desert. He told me simply to give thanks to Allah.

Before leaving, I went in to settle up with station owner and he also would not take any money and said it was his fault for not having enough fuel for me. The food and drink was a gift to a friend he said.

It was one of the wonderful moments of travelling through Mauri and I felt very guilty for blasting through their friendly country and not spending more time there. Everyone I met in Mauri both South and North were very friendly and great ambassadors for their country.