The $170 ScanGauge II lets you to track your consumption in real time and makes you more aware of how habits like gunning the gas pedal and driving 75 mph wreak havoc on your mileage. It's akin to stepping on the bathroom scale every day instead of waiting for your annual physical to survey the damage. You can even have fun with the ScanGauge by using it to track your progress as you set higher mileage goals.