If you think back on all the mindless, ridiculous things you've wasted your money on over the years, it's amazing how far out of your way you'll go to save a buck on gas. It's a compulsion, really. GasBuddy knows this, and its app feeds that compulsion the way retired parents feed their adult children as though they're still teenagers.
You've got one-click access to a map of nearby gas stations and what each is charging per gallon. Lowest price wins.
See also: Gas Stations, Around Me, Cheap Gas!