DeHaan's rule of thumb: a driver must be saving at least five cents per gallon for every mile they drive out of their way to make it worthwhile.
Still, using GasBuddy.com or a similar service to plan your gas purchases can save you money. And you can realize significant savings on longer trips because prices vary over greater distances and you'll be buying more fuel.
Other gas price services include Gas Guru, which uses data from credit card swipes obtained through the Oil Price Information Service and Wright Express.
The Gas Prices Map App at the search engine Bing.com provides gas prices within a 5-mile radius of where a person is searching, also using data provided by OPIS.
The navigation app Waze uses real-time traffic updates from other users to help you steer clear of traffic snarls. It also helps you find cheap gas stations.
The Cheap Gas! app uses GasBuddy.com data, but also provides directions to the gas station you choose.