first i'll address the bug. are you using sqlce 3.5? I'm pretty sure the rom i have came with 3.0 but I've since installed the latest 3.5. that's my best guess.
I enter 1 sample fill up. I get the same results before/after app exit & before/after reset. the next fill up gives "Error - Please enter a new mileage" click ok, then " - FormatExeption" .
glad you asked.
I think I may as well make a list. I went looking for a screen shot of something close, but couldn't find it.
1. obviously the interface.
a. I think the starting tab mpg info could be condensed and displayed with new entry tab, to make it easier. (actually maybe a tab per vehicle, other functions in a menu)
b. look at past info and guess the milage based on # gallons, quick adjustments for accuracy (arrows or 100/25/5/1 increment buttons) or just show the last info so you don't need keyboard/sip
2. fuel type & price fields (also remember previous)
3. ultimately it would be great to track air filter and oil change, with a reminder when it needs changed.
4. obviously some sort of export to csv/excel/ect... (import too I guess if ppl want to make changes or merge previous logs)
anyway, I don't want to overwelm you, but like I said I have yet to see an app like this fully mature. best of luck!