Fuel Efficiency Centers recently announced their new Fuel Efficiency Advisor – an intelligent gauge that accurately monitors fuel efficiency, suggesting that “consumers can plan on earning back the cost of their device in 12 short weeks”. That’s a pretty impressive claim, considering that it costs $159. Is it true?

The device (and others like it) can, in fact, monitor your mileage both short and longer term. It includes a powerful trip computer and can display quite a bit of information about your car. It does this by plugging into your cards OMBD11 port – a standard diagnostic port available on most cars built after 1996.

The device itself does nothing to improve your gas mileage. Your mileage will only improve if you use it as a guide to modifying your driving habits. It can help you choose more efficient routes on a commute. It will demonstrate clearly why jack-rabbit starts, frequent braking and higher speeds reduce your mileage. A good mileage gauge can improve gas mileage. Ask any Prius owner: their glitzy mileage charts make fuel efficiency a game – where winning consists of getting over 50mpg average on a tank of gas.

The key question is: can you really improve your fuel efficiency by the way you drive, and if so, by how much?

• If you’re already driving efficiently, you are unlikely to see any major benefit using this kind of device.
• If you aren’t willing to change your driving habits, this device won’t help you at all.
• To actually pay for itself in 12 weeks, you need to be driving a car that drinks a lot of gas. Assuming you actually get a 20% improvement in efficiency, this represents an increase from 12 to 14.4 mpg. The higher mileage you already get, the longer it will take for this device to pay for itself.

So who should get one of these devices?

If you want a great trip computer or have a compulsive need to be able to monitor everything going on inside your car, these devices are great as they can read your cards diagnostic port. They can even come in handy at diagnosing problems without a visit to the dealer.

If you’re a really bad driver and want to improve, these devices will give you feedback that can help you do better. If you are driving a larger car or SUV that gets relatively poor mileage, and put in the effort, the device really will pay for itself – possibly even in the 12 weeks claimed.

For everyone else: it may be a fun gadget, but don’t expect much in the way of savings.

Be sure to also check out the PLX Kiwi Scanner that provides similar functionality with a nice color/graphic display.