We don't have an official Facebook app yet, but I was able to add my fuel-ups to my Facebook profile with the Facebook
Import feature and my Fuelly vehicle's RSS feed.
If you want to try it out, first copy the location of your vehicle's Fuelly RSS feed. You can find that on your vehicle profile page under recent fuel-ups. Here's
what it looks like. Copy the feed URL.
Then log into Facebook and go to your profile. From there click the
Import tab and the
Blog/RSS link. It
looks like this. Enter your Fuelly feed URL, and Facebook will start importing your fuel-ups to your profile. It's not as fancy as a full-blown Facebook app, but it should work in the meantime.