I'm assuming the best way to purchase gas would be the gc from ppdg and then pay with a ink card earning 5x Vs. Using an exxon/mobile credit card which gets you the first 2 months 20 cents of the gallon, and then after that with 6¢ of the gallon and double plenti points with each gallon, instead of one per gallon 2 points per each gallon?
Also calculating the cash price when using the gc from ppdg it will probably be a huge difference in savings? (assuming the prices are not the same for cash and credit.)