Just one quick thing, after adding your fuel-up there is a screen that pops up. I like that screen, but can you possibly make the button to close it a little noticeable? Maybe a large black X in the top right (where most people go to close windows). The dismiss button can be easily missed.
Awesome site! Sure beats using my 12 page spreadsheet
I preferred the old look. In particular, the percentage of city/highway makes more work for me, and you've put it in a hard place to ignore; right beside it, another useless piece of info - number of fill-ups, and both are very large. Fuelly is for fuel economy tracking. Both the above distract, first by existing at all, and second, by being in a hard place to ignore. If you put them at the bottom of the page, I can tolerate them.
I would have preferred a check box for when I switch tires from summer to winter and back, since diesel fuel also changes energy capacity at that time - useful info for me.
Not being able to see the notes without mousing over them means I won't be using them again. A step backward.
The site is less elegant, and more bloated, in my opinion.