Just an idea, don't know if it's at all possible, or really that practical...

I was thinking it'd be cool to have a thing like the mileage signatures that could display info about how long it's been since you last filled up, for those that log their mileage to the database for every tank of gas. There could maybe be a box that could be checked if that's the way you log data... adding a date of fuel purchase somehow would make for more accurate readings... there could maybe even be a table of average time between fill ups? For example, for me it'll be 4 weeks tomorrow since the last time I had to fill up (though, admittedly, the time previous to that was only 5 days before), I think that's rather impressive, something else to brag about.