"This can be a way to basically get money back with purchases you're going to make anyway," says Greg McBride, senior financial analyst with Bankrate.com
McBride says rewards cards are only for people who pay off the balance in full each and every month. If not, it's a losing proposition.
"The interest charges are going to outweigh whatever you would have earned on the reward. Instead focus on cards that have the lowest possible interest rate," he says.
There are lots of gas reward credit cards to choose from. Find the right card and you can easily cut your fuel bill by as much as 3 percent to 5 percent.
But you need to understand the rules before you apply for a card.
"Some of these bonus pay-outs for certain categories like gasoline and groceries require you to sign up in advance and they may only be in effect for three months," says McBride.
In addition, he says, "Some of these categories rotate every three months. You may see an advertisement for up to 5 percent back on gasoline purchases, but that may not be year-round. It may only be in effect for certain period of time."
And some of those payouts may be capped per quarter or per month.
You can compare these cards at sites such as: CardHub.com, LowCards.com, Credit.com, NerdWallet.com and Bankrate.com.