Road Test of 4 Fuel-Efficiency iPhone Apps

Lately it seems the only thing more dependable than the force of gravity is the inevitable rise in gas prices, which seem to be resisting the force of gravity altogether. And this has frugal drivers squeezing every last mile from an increasingly expensive tank of fuel.

Of course, now there's an app for that. In fact, there are several apps that can help you gauge your car's fuel efficiency at every fill-up, track monthly fuel costs and even store relevant data such as your car's correct tire pressure. To help you decide which of these apps are best, we tested four of the most popular ones for the iPhone.

Accufuel
Grade: A-
Price: 99 cents
Pro: Easy-to-read graphics
Con: 2011 model cars not yet supported
Compatibility: iPhone, iPod touch, iPad

One of the things we immediately liked about the Accufuel app is its great graphics, which give an excellent, one-glance overview of a car's fuel efficiency. On either side of a gas pump icon are mpg numbers for both the last fill-up and overall average. Tap the pump icon to input all the relevant info at the next gas station stop, selecting whether you're adding a few gallons (while you await payday) or filling the tank completely. An easy-to-read graph also shows mpg over a period ranging from one month to two years.

Swiping to another screen allows you to check the fuel mileage numbers of multiple vehicles, which can be added with a tap of the "i" (for info) icon. Just find your vehicle's year and model and add it to the list. But if you have a 2011 model, you'll be disappointed. As of this writing, new vehicles — such as the 40-mpg-plus 2011 Chevy Cruze Eco that we used to test this app — are not yet listed. So we chose the Cruze Eco's predecessor, the Chevy Cobalt. Another ding on the app is that once you select options like "miles" or "kilometers" and "trip" or "standard" odometer in the settings menu, you can't change them.

Other elements of the app offer greater flexibility. Tapping the "i" button gets you back to the vehicle list, where you can view your entire fill-up history, edit previously recorded fill-ups or even add a fill-up you forgot to record. From the same screen, you can also export your fill-up data via e-mail or "export to import" in a proprietary file managed on the developer's Web site (registration required).

CarEconomy
Grade: B
Price: Free/99 cents (premium version)
Pro: Plug and play
Con: Only measures average MPG (and current MPG with premium app)
Compatibility: iPhone, iPad, iPhone touch (with GPS adapter)

CarEconomy by DriveGain kicks things up a notch by using the iPhone and iPad's GPS capabilities to automatically track fuel efficiency as you drive. While other fuel-efficiency apps require you to input your odometer reading and how many gallons you've added, the CarEconomy app lets you just select your vehicle and drive. It's a simple, straightforward solution and we found it accurately tracked a Chevy Blazer's fuel usage.

But if you're looking for a deeper database with elements like fuel-efficiency history or cost per mile over the last six months, you'll find your expectations running on empty. And as easy as it is to use, we found that with CarEconomy, we missed all that extra data and information.

We also don't like the ads that pay the bills for this free version. So we advise upgrading to the premium version, which enables two additional features. One is an "instantaneous fuel economy meter" (CarEconomy's term, not ours), which gives you immediate mpg gratification by showing your current fuel efficiency on a color-coded gauge. (A plus is that the app supports both U.S. and metric measurements, so the meter will use the same gallon/metric calibration you selected in settings.) The second is an iPod controller that you can toggle off and on.

Fuel Economy Calculator
Grade: A
Price: 99 cents
Pro: Deep feature set
Con: Requires complete tank fills to work accurately
Compatibility: iPhone, iPad, iPhone touch (with GPS adapter)

The Fuel Economy Calculator is a geek's delight and a go-to app if you're all about deeper data and cool gauges and buttons. The app even features a vehicle profile area, where you can note your correct tire pressure and recommended motor oil and insert a photo of your ride.

These extras are nice details, but what we liked best about the app was its depth of information, including comprehensive fill logs and averaged results such as fuel cost per mile, fuel cost per month and farthest distance traveled between fills. The app also gets bonus points for its cool design. It feels like a small digital cockpit with all the aforementioned gauges and buttons to tap, as well as chrome-color borders and auto-scrolling instructional text. The app also offers a helpful informational screen that gives you tips such as how to delete and edit previously recorded fills.

Another road-worthy feature is the journey cost calculator. Input the distance you'll be traveling and the app automatically estimates your fuel bill based on previous trips. Like other apps in the category, the more data you input (i.e., the more diligent you are about logging your fills), the more accurate and useful the output. You can also enter multiple vehicles and choose between U.S. and metric measurements.

Gas Hog
Grade: A-
Price: 99 cents
Pro: Zero learning curve
Con: Ultra basic
Compatibility: iPhone, iPod touch, iPad

Spare and efficient, Gas Hog is skinny on bells and whistles. If you like charts and graphs, you'll be disappointed, but with this app, you will get simple and fast readouts that give vital stats like the fuel efficiency of the last fill-up and the historical average.

Gas Hog has three basic screens from which to choose: log, stats or tips. Select log and tap the plus sign when you're at the pump and you'll see fields for your odometer reading, amount of fuel added, cost and any notes you might have ("Gas has gone up again!"). The date appears automatically. Once you've been using the app for awhile, all your logged refueling stops will show in a long scrolling screen, giving you total miles, dates, amount of fuel pumped and mpg.

The stats screen shows fuel economy history, automatically calculating the last tank as well as multiple time periods, including the last 30 days, the last six months and an overall figure. You can also view cost per mile for both your last tank and the last 30 days. The tips screen brings you a list of no-brainers like "Carrying excess weight can reduce your fuel economy."

The settings screen has three separate input fields to calculate distance, fuel and economy. In settings, you can also choose between U.S. and metric equivalents, including miles per gallons or kilometers per liter. You're also given the option of exporting data to e-mail. Like the other apps we reviewed, Gas Hog lets you add additional vehicles.