With the release of iPhone 2.0 came a torrent of new (Apple-approved) 3rd party applications, among them several focusing on car fuel efficiency.  These are for the folks fortunate enough to own an iPhone and yet not yet ascended to the hallowed plane of hybrid ownership.  Here’s a rundown of those I could find — I haven’t tried them all out, yet, and would be curious to hear your impressions.  Some of these definitely seem better executed and more attractive than others.  (Note also the curious prevalence of WikiWord naming.)

With the iPhone platform there is definitely a lot of potential for bringing these types of tools into the social sphere - each of these could be turned into interfaces for web-based hypermiling competitions with friends, for example.

AccuFuel

As with all of these apps, AccuFuel focuses on changes in your odometer and the amount of fuel you get at the pump. I have played with this one a bit. It has a nice widget feel to it - simple interactions and easy data entry. You can set it up to track mileage for more than one car and flip through them just as you can flip through multiple cities in the iPhone weather app. This is more graphical than most - trends over multiple time frames are shown graphically. By Appigo.  ($.99 in iTunes)

Car Care

From the look of it, this app gives you a little more power, if you want it. It does a little more than mileage tracking - you can use it to set car maintenance reminders, which may be handy if you base such things on distance driven. It looks like there’s a little more granularity for those that want it - you can track city vs. highway miles, regular vs. super/premium fuels, and price. There is an import feature if you’ve been keeping data on your computer. This one also has a little visual design and a graphical trending screen. By KB Productions. ($4.99 in iTunes)

CarStat

CarStat uses more of a tabular layout and straight-up data entry approach.  I appreciated that CarStat starts up with some “dummy” data to show me how it works right off the bat.   I think that some of the interactions, such as the way the user calculates averages and totals, could be rethought to create a more fluid experience.  Calculation is naturally at the core of these types of applications, but I think moving these concepts beyond numbers — and into the experiential — is important. By Cogstorm. ($1.99 in iTunes)

FuelGauge

FuelGauge has a pretty attractive home screen (below) showing how my energy use is trending.  There are a few things about FuelGauge that remind that sometimes precision and power don’t always improve the experience — for example, telling FuelGauge I pumped 5 gallons takes 7 taps - some of them zeroes in “5.000″, since FuelGauge always wants its values to the third decimal place.  I expect for an app like this, I will usually want my interaction to be as quick as possible.  But it seems the developer of FuelGauge is putting a lot of attention into future iterations of the app so it may be one to watch.   By iphonecodemonkey. ($.99 in iTunes)

GasHog

Like CarStat, GasHog uses more of a tabular layout and straight-up data entry approach. I have not tried it out, though from the screenshots, it looks executed smartly, if a little dryly.   Again, I think moving these concepts into the experiential is important for engaging a lot of people.  Only geeks like you and me will really put up with a ledger book approach.  By Adair Systems. ($.99 in iTunes)

Miley

I haven’t tried this one out, but it looks like it has a little character and playfulness to it.  As we’ve seen here on Green Interfaces, fuel economy calculators don’t tend to have much of a human touch, so I like the effort.  Reviewers in iTunes also comment that Miley has great tips for helping improve economy, giving it an educational function that some of these lack.  By BunsenTech. ($1.99 in iTunes)

Mileage Tracker

Mileage Tracker seems to have gone a similar route as CarStat and GasHog - tabular data entry interface.  By Lemdisyn.  ($.99 in iTunes)

Tankbuch

Tankbuch comes from developers in Germany, and is available in English, French, and German.  It has the added advantage of being free - but users in the United States will probably not find it usable as only km/l units are available.  By osXwerk.  (Free in iTunes)