It can't be true. If you look at their detail page....
http://www.fuelly.com/driver/imtrevonte/vehicross
You'll see their is no consistency. Everything from 3.7MPG to 57.1 MPG is listed!!! WTH!!! It would seem he/she may not enter or understand the site correctly -- as this type of variance would be impossible.
I think it's a good site. OTOH, unlike Kat's forsale check list, it lacks the details I feel are important. If you're wondering what I mean, refer back to my first post in this thread -- where I talk about the details I feel are necessary to make any type of vehicle-to-vehicle comparison.
From what I see, The fuelly site is a reasonable tool to confirm/deny EPA estimated fuel ratings.