Metro best 'out of box' mpg vs others?

[stillsearching]

I currently have a Saturn SL which gets me about 38mpg highway and 29 city.

I'm looking to substantially improve this without getting into something radically unreliable (sorta defeating the point) or needing radical mods out of the box. I eventually will probably do boattails and such but for now I just need something with better mileage, so that the money saved can be applied to those mods later.

Modifying the Saturn is one option, but others suggest just getting a different car that is naturally more efficient.

The Geo Metro Xfi's used to get 55mpg (a friend had one) despite driving 75mph highway and would get like 40mpg city. I was given the impression the newer ones got less due to more weight and engine changes. Are there any other cars almost as good stock to get 40mpg city and 55mpg or better highway, "normally driven"?

What about once modified, both mildly modified and wildly modified, do any 'beat' the Metro or for that matter match it?