AMEX Blue Cash Preferred gives 3% cash back for gas. However, if your local grocery stores sell gas cards, then you can get 6% cash back that way. My local grocery store has gas stations at many of its supermarkets. Not only do I buy its gas/gift cards and get 6% cash back, this chain offers an additional .03 off for using their gas/gift cards. So, basically I am getting 7% off (at least until AMEX starts limiting how much cash back you can get via groceries next year).