I just started using GasTracker on my iPhone 5. So far I haven't had any problems other than my average MPG on the Fuelly site shows 33.9 while on the GasTracker app it shows 32.0. Everything else matches correctly. Not a big deal but wanted to let you know.
Actually this was caused by my not reading the stats on the site correctly.
I track my Odometer miles and not Trip miles, in the past, the app calculated my trip miles and displayed them on my iPhone. With one of the recent updates it just started showing the odometer miles and not the trip miles even though I have always entered my mileage by odometer. On the Web page it still shows the miles between fill-ups. I am afraid that if i change the setting on my phone to show the trip miles that the first fill-ups will not show a correct mileage.
I have almost the same situation as Bradherr. On all my vehicles using my iPhone app, I was only allowed to enter trip miles. This was fine with me. Recently this was changed to only allowing me to enter odometer readings on my iPhone and now I had to go back on all my vehicles and manually re input trip readings thru the website to get a proper MPG. This being said, only one NEW vehicle on my iPhone allows odometer readings thru the iPhone app. So, in closing...using the iPhone app i can input only odometer readings, but all of my vehicles except one will display incorrect MPGs thru the website. Only one vehicle uses odometer thru the app. iPhone 5s running ios 7.