Gunna have to agree with the 5 speed cavy idea they usually get pretty good mpg. Just be careful when you buy to make sure it dosen't need a lot of work and make sure its been taken care of well. My fiances old Cavy gets 21 mpg which is sad because my truck gets 16-18 lol and here v6 taurus gets 25mpg. We still can't figure out why its getting such poor mpg for a cavy.

 

sounds like its got bad fuel pressure if only 21mpg. but a cavy is a good idea.

 

Cavy's aren't a bad way to go.With a 03-05 they have the 2.2 ecotec it will have a little power an should get around 30-34 mpg.I've seen them for really cheap lately too.Just expect to throw brakes an wheel bearings at them a lot.That's the only thing we ever really had a problem with(other than the one's we cause with modding it)
We haven't had better than 25mpg out her's the last few years now that it's making 100 horse more at the wheels than it did at the crack.