This in unconfirmed, but the idea is as follows:
I heard that if you buy GC at BP Gas, then use them to pump, the rate they charge you is the cash rate, not the Credit Card rate.
If this works I would go in buy $1500 of these cards, on my Freedom card as well as my wife.
1)I would have the first $1500 spent on the card is on gas... with 5% back.
2) I would get gas at the cash rate VS. the Credit Card rate.