What Is The Best Mobil Fuel Card?

What is the best discount card at Mobil for 91 petrol for household car use? FnF/Skeggs, RuralCo or Costdriver? or other fuel card?
I am currently using a FNF/Skeggs Mobil fuel card which gives 7c per litre plus 1c (?) to a charity that I have chosen but has $10 joining fee and $6 card fee. But I now see the Costdriver Mobil fuel cards get 9 cents off per litre with no annual or card fees. I see the RuralCo card has 12c per litre but I would have to be a farmer or working the land to join so unfortunately take counts me out for that one.

What are people using for 91 fuel and what is the discount?
Anyone have any experience with CostDriver?
Anyone joined RuralCo without being a farmer?