Go to the fuelly page for the vehicle that you want. At the bottom under the graph and the log book will be a row of icons. There'll be icons for Facebook and Twitter, and a yellow badge/shield shape like this: Click the little shield and get to where you can copy the text to add to your forum posts, or put in your sig.
It has been quite a few years But I thought that PC__ or GREENHYBRID had a "garage" where you could log your fuel usage?? maybe its faded..