I saw Twitter buzz building this morning over Fuelly, a site that records your gasoline purchases and gives you potentially useful info in return: your car's mileage and cost data like dollars you're spending per mile and your fuel economy over time. You can record your info on an iPhone, even. The site's special sauce is the social angle; you can follow people and compare your mileage to theirs. Coming soon to the service: A way to update your gas purchases over Twitter.
Believe it or not, there are already other Twitter-enabled gas purchase trackers out there. MyMileMarker and FuelFrog both let you Tweet your receipts, so when you visit your account later from a big computer you can analyze your driving and expenses.
Those sites don't have the social angle that Fuelly does, though. With Fuelly, you can compare and compete with other users for mileage bragging rights. Does that matter? It could help you research real-world mileage on a car model you're thinking of buying. And it might be something you want if you're a competitive hypermiler. I can't imagine the novelty of Fuelly's social network becoming something you'd actually want to stick with, but if you use the site for tracking your personal mileage, it's a gimme.
Fuelly also serves to remind us that there are a lot of resources to help us track our gas spending and save money. In addition to the sites mentioned so far, there's also FuelEconomy.gov's Your MPG, which does mileage tracking using a retro, hideous K-Car-era interface.
The iPhone app Triplog will do the useful mileage calculations as well as track your car use for tax purposes. iPhone users might also want to check out lower-cost apps like AccuFuel, FuelGage, GasHog, and CarStat.
To get the best prices on gas, there are map sites like GasBuddy. Sadly, none of the mileage tracking sites yet integrate with a gas price database like this. And do keep in mind that driving a few miles to save 10 cents on a gallon of gas might end up costing you more than you save, not including the cost of your time or extra wear on your car.
If you really want to save money on gas, drive mellow and inflate your tires to their maximum recommend pressure. Thanks to the Obama/McCain energy spat it's become cliche, but I just corrected the slightly saggy tire pressures I was driving on and my mileage went up 15 percent. No iPhone or Twitter widget is going to save me money like my gas station's air hose just did.