Reimbursable business expenses are one of the best ways you can rack up bonuses from rewards credit cards. Today's most competitive gas rebate cards can convert your fill-ups into a source of extra cash:

If you really intend to use a dedicated rewards credit card just for your gas purchases, you'll love this deal from PenFed. This card's 0.25 percent rebate on everyday purchases isn't much to write home about. However, a whopping 5 percent rebate on your "pay at the pump" gas transactions can make you feel like your company's giving you a raise.

Although PenFed's credit union charter was designed to serve military personnel and their families, you can qualify for membership by making a one-time donation to an affiliated non-profit organization.

If you think you might occasionally use your rewards credit card for more than just fill-ups, this credit card for excellent credit offers a 3 percent rebate at all U.S. stand-alone gas stations. U.S. stand-alone supermarket purchases count toward a 6 percent rebate (for up to $6,000 in transactions per year).

You can cut your employer in on some savings if you happen to hold a Costco membership card. American Express matches the 3 percent gas rebate from the Blue Cash Preferred card, but includes the gas stations attached to Costco warehouse clubs in the deal. Since Costco discounts gas by a few cents per gallon compared to stand-alone gas stations, you'll save your employer some cash while still earning an annual rebate.

Pentagon Federal Credit Union and American Express both offer credit cards for excellent credit. If you've got a few dings on your credit report, but you still want to get a great rebate when you pay at the pump, check out Chase Freedom. Chase offers versions of its flagship cash back credit card for consumers with average credit. Although you'll earn just 1 percent cash back on your gas purchases throughout the year, Chase offers quarterly promotions that can ramp that reward up to 5 percent.

Although you may see some gas credit cards advertised with stronger rebates and perks, remember that you could end up paying more to fill up with a preferred brand. The gas rebate cards on our list let you earn rewards just about anywhere.