As noted, the trip was not up and down Colorado mountains, but across Nebraska and Iowa. The eastbound leg may, or may not, have had a bit of a tail wind, but nothing major. Our 24' MH is very aero designed, no overhang over the cab. I've been recording our gas purchases for the entire time we've owned the MH, and the MPG and fluctuations have been very consistent over the years. This trip is a perfect example: from 7.8MPG to 9.7MPG. We always try to drive at the posted speed limits, if the wind conditions and the terrain allow. As Turner,P. posted our MPG is usually between 8 and 9 MPG, but we never got to 10MPG.