You could just get a store giftcard for the gas pump. For example, Safeway/Von's giftcard and use the giftcard at the pump. Earn 6% still since the purchase occured inside the store. YMMV depending on which brand you use, but this works at my Safeway gas. Still the $6k cap though on grocery purchase.

There is also the Blue Cash card. Unlimited 5% at gas pumps and groceries after $6.5k initial purchase.