FYI, that's not my graph - it's this guy's:
Speed vs. Fuel Economy - 2004 Chevrolet Aveo sedan (1.6 L, 4-sp automatic)- EcoModder.com )
He measured those MPG values doing 2-way runs at each speed indicated. So they represent what your car would be getting at that speeds on a level road - it doesn't take into account the fuel used getting up to that speed, different weather conditions, etc.
His actual fuel log from EcoModder shows tanks in the low to mid 30's:
You CAN get tank to tank MPG in the 40's with an Aveo, but not likely with the automatic. You'd need the manual for that, very careful driving techniques and a MPG-friendly commute.