(April 22, 2011) SANTA MONICA, Calif. — As gas prices and environmental concerns become bigger issues for American drivers, new iPhone apps are now offering easier ways to monitor your vehicle's fuel efficiency, according to Edmunds.com.

"These apps can give you accurate feedback on how much gas your car guzzles by inputting the mileage and the amount of fuel at every fill-up," said Doug Newcomb, senior technology editor at Edmunds.com.

"By keeping a running tally of your car's fuel economy, you can not only save yourself some money, but you'll be much more conscious of the energy resources that you consume on a daily basis."

Edmunds.com evaluated four apps designed help drivers get the most out of their fuel tanks:

Fuel Economy Calculator (99 cents) — This app impressed Edmunds.com with its depth of information, including comprehensive gas fill logs and outputs such as fuel cost per mile, fuel cost per month and farthest distance between fill-ups. The app's "journey cost calculator" estimates your fuel bill for upcoming trips, and the vehicle profile feature can also remind you of your car's correct tire pressure and recommended motor oil.

CarEconomy (Free) — CarEconomy by DriveGain employs your phone's GPS capabilities to automatically track fuel efficiency as you drive, which means the user does not need to input odometer readings and gallons of fuel pumped on each fill-up. An upgrade to the premium version (99 cents) does away with the app's ads and includes a color-coded gauge offering immediate feedback on your car's fuel efficiency

Accufuel (99 cents) — The most visually compelling of the apps tested by Edmunds.com, Accufuel offers an easy-to-read graph showing mpg over a period ranging from one month to two years. This app also allows the user to check fuel mileage numbers of multiple vehicles. One drawback: at the time of Edmunds' review earlier this month, many 2011 model year vehicles had not yet been added to the app's roster.

Gas Hog (99 cents) — Gas Hog doesn't have the graphs and charts that other apps have, but it offers simple and fast readouts with vital stats of your car's fuel economy, such as cost per mile for your last tank and/or the last 30 days. Data can also be exported to e-mail in case you want to keep records on your home or business computer.

More details on Edmunds.com's tests of these four fuel-efficiency apps.