You can't upgrade from Exxon Gas Card into Exxon Mastercard and they issued by different creditors. Exxon Gas Card is issued by Monogram Credit Bank of Georgia Exxon Mastercard is issued by Citibank(SD),NA. Ron.
One doesn't care about the other ... I've had a Mobil card for 12+ years and it didn't help. That's why I switched to Chase/Shell MC. They offer better rebates anyway. -mj