anyone else getting really random displays? normally a full tank'll display around 420 miles for me, but there're times (like this past fill up) the range'll be about 390 miles. same shell gas station, always at night, always 89 octane. i can understand a 10 mile difference, but a whole 30? i mean granted, the computer's calculation might be a little whack, but to have completely different range of miles left on a full tank seems a bit odd.