27-29 sounds normal to me for 75 mph on the freeway, with some city thrown in there.

Official MPG ratings for the '09:

2009 - hatchback and sedan

(City / Combined / Highway)

5-speed . . . . . . 27 / 30 / 34 MPG (US) - EPA
automatic . . . . . 25 / 28 / 34 MPG (US) - EPA

from http://www.aveoforum.com/forum/f106/...u-s-epa-10139/

You haven't said if you've got th automatic or the manual.

As others have said, the biggest freeway fuel savings come from slowing down.