Diesel in Iran is less than 2p per litre. That's about 3 USą per litre. So, after filling the fuel tanks, sink, pans and cups, the truck was pointed north into Armenia.
The Iranian-Armenian border had been closed for many decades. However, it's now fully open, with many oil tankers and containers crossing daily. Two completely different crossing philosophies. For the Iran part of the crossing, you can leave your wallet in bed. When you get to the Armenian side, it should be fully awake, and have just come back from a top level meeting with a cash machine.
As you go north, prepare yourself for the most spectacular roads in your life.