Free printable gas coupons are not available online. Instead, the best way to save at the pump is to enroll in a gas station's rewards program or apply for a gas station's credit card. Coupons are available for auto repairs done by gas stations, accessible through discount websites like Retailmenot.
Exxon-Mobil, Citgo, Shell and BP all offer ways to save on gas. Exxon-Mobil's Plenti rewards program allows members to earn points on gas purchases, as well as purchases from retailers like Macy's and Nationwide. They also offer a credit card that provides a 6 cent discount per gallon when used at the pump. Shell has partnered with regional grocers for their version of Plenti, while Citgo and BP also offer discounts through a credit card.