My 1976 F does 150 kts on 9.5 gals/hr. The older E and C models are a
little faster because they have shorter cabins. I've sat in the back of
mine with another full size guy. Its not like a full size BMW but
better than a 172. If you are comparing a 172 with a C you'll end up
going MUCH faster in the C for about the same purchase price.

-robert