Yes, you can get gas with your Fancard! However, we highly recommend you simply go inside and pay in advance of filling your tank.
Because the gas station may pre-authorize the card for an amount ranging from $50 to $100, and you must have enough money on the card to cover the pre-authorization. Once you are finished at the pump, you can request that the merchant charge the card for the exact amount and release the pre-authorization, but it is not guaranteed that the merchant will honor the refund request.
So to avoid any holds on your account, we suggest you prepay inside.