Fuelly is a site that tracks your gas mileage over time and gives fuel-saving advice. This is the basic knowledge you need to make fuel-saving changes.
Once you complete the free sign-up, you add a car or motorcycle to your profile. You can track of miles driven between fuel-ups using your car’s trip meter, or record your odometer at each fuel-up. You can download your data and discuss it on the Fuelly Forum.
The information is public and shared between users to make it easy to compare how your vehicle performs compared to others. It’s also a good resource if you are considering buying a car.
There’s a short “how to” video on the site.