I use Shell 9/10 due to the fact they offer a Shell Savers Card (save from 2 cents off per gallon up to 22-25 cents when their Shell Racer wins a race) already happened 4-5x this year.
They now have the FRN (Fuel Rewards Network) also linked to your card of choice and whenever you use your card (outside of gas) you already earning points for gas.