I haven't install it yet.

Crashes on iPhone 6+ too. See post in v3 sticky. Good luck in getting a fix ;)

From a fresh install, opening the program for the first time, it goes to the white screen with this versions changes. Then it crashes. Reopening it opens to the login screen. After 3 mins of syncing data it has a continue button on the bottom. Click continue and it crashes. That's as far as it will go.

iphone 4 IOS 7.1.2 same issue here since the update, I can't access to the app crash all the time.

Exactly the scenario I experienced on my 5s on OS 7.
Very aggrivated and disappointed.. This was a forced update and now I'm stuck... Right before a weeks long road trip out west.... :(

Is there any way to roll back to v2 ?

No; Apple does not permit such an action.

Unless the data on the Fuelly website is altered for v3 there is a pain in the *** way to go back to v2. If you have a backup of the v2 file you can do several steps to get it back, do an internet search for it.

iOS 7 on a 4s.... closing all the apps in the background (nothing running), it crashes right away, and all you see if you bring it up from the background (it's running there, just sitting), it shows the what's new screen, well part of it anyway - I assume there are controls to acknowledge the what's new screen - but then immediately drops to the background... won't stay running in the foreground - just floats around. you can run other apps and have them in the background there too - this one just doesn't stay in the foreground long enough to try and even figure out how to acknowledge the what's new banner (you see maybe 2/3 of the banner)

I'm having the same crash on startup problem on my iPhone 4, with no further response from Robert after an initial email. I see there's another new version at the App Store, but it doesn't address this issue.

I've reverted to 2.1, which continues to work well.