It's a PHEV, but my Ford C-Max Energi will do over 600 miles on the 14 gallon tank in long distance driving (full charge gets you 20ish miles of stop and go, or 5 miles of highway, so basically doesn't matter). I'd guess the HEV version should do better, as it has less battery weight, but is otherwise pretty similar AFAIK.

Many cars have 16-20 gallon tanks, so a 14 gallon is fairly small (although 600+ miles is plenty)