If you want the Ferrari of fuel economy vehicles, get an Insight. (5MT only!)
A modded one will give you 80-100 mpg all day long at 50 mph on a level road in good weather.
Some will warn you of high repair costs, but at the age & price of those cars, you'll be prepared to drive one with crunchy 2nd gear synchros and a dead (or weak) hybrid pack. I didn't really have to put a penny in my 2000 Insight in the 2 years I owned it.
Highly entertaining to pilot one, managing its various systems for best effect.
Have you seen this thread?
http://ecomodder.com/forum/showthrea...ems-18892.html