Im driving an '02 Echo, with a good list of mods, and in rural driving conditions. Lots of highway, with 30% city or so. Biggest mod is killswitch, but I don't use P&G.
I managed 551.7 miles on 10.8 gallons, giving
51 MPG 
And this is WITHOUT these major planned mods:
-full bellypan (big deal on these echos)
-Kammback
-Front wheel covers&skirts
I'm pretty stoked for what is to come!