Rather than driving five miles out of your way to save a penny or two per gallon, you can generally save between 3% to 5% on gas if you keep the right credit card in your pocket. At $4 a gallon, that's the equivalent of 20 cents off per gallon. Even if gas goes back down to $3 per gallon, you are still paying the equivalent of $2.85 a gallon.

If you already pay with plastic, you can check your credit card statement to see how much you are paying per fill-up and go from there. If you are filling up every two weeks that translates to 26 fill-ups per year, so the amounts can add up quickly.

For Penny Pinchers

Discover's Open Road card pays you 5% cash-back on auto-related purchases up to $100 per month with no annual fee. After that point, you'll start earning 1% if your spending exceeds $3,000. Between $1,200 and $3,000, you are earning either 0.25% or 0.5% Confused?

To make matters more complicated, Discover apparently will let you have more than one Open Road card, so a couple, or one person with two cards, should be able to get 5% back on $2,400 worth of gas purchases per year, with no annual fee. That translates to either $60 cash-back per year for a single driver or $120 for a couple with two cards (or Mr. I Have Two Cards).

Even if you go slightly over the $100 per month barrier, this card is the best option for most drivers, (including yours' truly.) It's not until you spend $175 per month that the other cards start to look more attractive. Although yes, with gas slowly inching up to $5 a gallon, everyone except Moped drivers will easily exceed that limit.

Discover also offers cash back in varying amounts on certain online purchases at places from Blue Nile to Bed Bath & Beyond to Best Buy. You can use your cash back to pay your credit card, or to get additional cash rewards at certain retailers. But we're only talking about $60 a year for most people, so don't overthink it (because I already did.) But for a family with three or four drivers, you could save a fair amount of money if all you do is put gas and oil changes on this card, and you do get 1% back on other purchases.

Middle of the Road

The aptly-named Chase Freedom card offers 3% cash-back on your top three spending categories. Assuming that gas is one of the top three (which it probably is if you're still reading), you start earning more cash back per month than the Discover card when you are spending $250 per month.

While that may sound high, for a family with two cars or more cars, each getting filled up two to three times per month at $50 per visit to the pump or more, you are probably paying $250 a month whether you realize it or not. You also get a $50 bonus when you reach $200 in rewards, but that would mean spending $6,000. You can also switch the card to earning miles if you suddenly find yourself having too much cash (and please give me a call if you need any other ideas.)

*Note: Chase is currently offering a $50 credit for those who sign up, so that skews the math somewhat lower, but only for the first year.

For Costco Members' Only

American Express offers a Costco card that pays 3% back on gas and restaurants with no annual fee. Since Costco does not take other credit cards, and generally has fairly cheap gas, this can be a good option for you if you live or work near a Costco with a gas station and already have an annual membership. It is probably not worth joining Costco for $50 per year just to get 3% back on gas, as you'd have to spend $1,600 per year or $133 per month on gas just to break even.

For Really Big Spenders

The American Express Blue Cash card offers 5% cash back on all gas purchases -- but only after you spend $6,500 each year. In other words, for the first $6,500 you spend, you'll only get 1.5%, which translates to $97.50. But after that, you'll get your unlimited 5% back. At that rate, you'll start making more than the Chase card once you hit $12,000 per year. This card makes sense if you know you are going to put a huge purchase like a trip or a huge TV on it to get you past the $6,500 mark, or if you spend more than $1,000 per month in gas.

Monthly Gas Costs	Annual Gas Costs	Best card for You
$0-$175	$0-2,100	Discover Open Road
$175-1,000	$2,100- $12,000	Chase Freedom Card
$1,000+	$12,000+	Amex Blue Cash

Always keep in mind, if you carry a balance on any of these cards at anything above zero percent interest, you will probably lose more money in the long run then you would ever gain by getting 20 cents off on a $4 gallon of gas.

Good luck!

Brett Widness is an editor with AOL's real estate channel, but he sits right near the Autos team.