I have noticed you have started changing the mileage listings which are not active to gray, I do like that change.....However, I have a suggestion for a more accurate data base or at least in my opinion more reflective of active users.

Perhaps you could do a couple of things, require at least 2 entries before showing a car in the database eliminating those that want to mess with the stats with 1 or even 0 tanks at 100 mpg or 12 mpg.
The other would be even more work, maybe have a "trip a" & "trip b" for each car with one being for active cars only (the black entries) the other being for all reported cars (the current data base).

I know that either of these would probably be a lot of work & well, frankly, keeping this site up and running is a lot of work but be aware, I for one really appricieate your efforts.