I bought my first diesel car last year, when diesel prices were over $4. But when I discovered inner-city gas stations were pricing it as low as $3.50, I decided to get strategic about fill-ups. GasBuddy lets you drop in your city, state or zip to “find gas” nearby, using crowd-sourced updates to keep the pricing current (each price shows how recent the update is in minutes, hours or days). It lets you filter by gas type (regular, midgrade, premium, diesel) as well as distance/price. In all my time using it (and several 10-hour cross-country trips) I’ve yet to find a bad reading, and though I sometimes have to zip a few miles out of the way to fill up, it’s helped save hundreds of dollars to date.
Link: GasBuddy