[evldave]

Great info. I just finished a 2200 mile trip from WA to CA and back again, mostly on backroads (actually 75% on backroads). Interesting to see the difference between a H3 w/o rack (yours) and H3 w/rack (mine). Here's my experience without the details (I'm too much of slacker to keep track of locations).

Tank 1 - All freeway, 75-80, 305 miles, 20.17 gals, 15.12 MPG
Tank 2 - all freeway, 70-75, 293, 17.8, 16.5 MPG
Tank 4, 25% offroad (w/Bebe, Sewie, the Bullies, and Racer), 75% 60-80mph, 178 miles, 13.5 gals, 13.2 MPG (note: this is wheeling and driving combined)

Next few tanks are mixed highway, offroad, and back country roads:

15.5 MPG
13.6 MPG
13.4 MPG

Then, interesting part here...I started full offroad, washboard, 30-50mph from Modoc NF up to Eugene, OR (via offroad, then 97, then offroad, then 58, then I-5). Once I switched to consistent offroad (or winding highway backroads), it went like this:

17.4 MPG
15.9 MPG
17.0 MPG

Without going into the detailed level, I'd say maximum MPG is achieved at 30-60 MPH, on mid-throttle roads that involve long stretches of medium throttle (w/ or w/o hills), and don't require lots of 4th gear (auto) driving.

Most of my driving was done under a lead foot, with a decidedly un-aerodynamic roof rack. I did get much better mileage on non-highway roads. Of course, look at it this way:

@ $2.95/gal (what I paid in Oregon). The difference in 1 MPG increase over 1k miles saves you $5.00. Does it matter?