Some upscale cars already are equipped with a feature I find most illuminating, a gauge that show how fuel-efficiently you are driving at any given moment. Stomp on the gas and watch the meter dip to 12 mpg. Bop along on cruise control at a thrifty 55 and watch it bounce up to 28. Make sure to look up at the road as well, though, or you may see it return to zero.
There are aftermarket options if you want to get serious about monitoring your fuel consumption in real time, a must-have for us tech-heads and a interesting option for any driver. The ScanGauge II provides the fuel consumption rate to the nearest 1/100th of a gallon while you drive. It also reports 11 other functions (engine load, battery consumption, coolant temperature, and a sobering cost per mile/cost per trip) and claims to monitor 25 others. According to Amazon reviews, the setup is easy enough for a non-motorhead to tackle. The Scangauge II sells for $159.95 on Amazon.
A new option, the PLX Kiwi, measures engine performance and fuel efficiency as well. However, it also includes a game-like feature, a series of driving challenges designed to help you learn to drive in ways that conserve gas. The company claims that by following the lessons taught a driver could save as much as $500 or more annually. An additionally benefit comes in the form of lessened CO2 emissions. The PLX Kiwi is on sale at the moment for $299.
Such devices might be especially helpful when installed on cars of novice drivers, who haven't yet made the connection between rabbit starts and gas consumption. And some people need a gauge like a dieter needs a scale, to track every little bit of improvement.