When it comes to using the card to help you build credit, Exxon Mobil isn’t clear on how effective their card is.  Their terms and conditions say they may report your activity to the credit bureaus—but they don’t specify which bureaus or if they report to all three of them.  That said, Citibank (issuer of Exxon Mobil) reports to all major credit bureaus, so it’s likely that Exxon Mobil can help you build credit if you use the card responsibly.