Proof that wind is the big factor in MPG.

I once spent a day dragging my TT across Oklahoma into a 50 mph headwind, something I will never attempt again, trust me. It is pretty flat across the panhandle of Oklahoma, and I got a whopping 9 mpg with a rig I'd just dragged across the continent and back for an average mpg of about 14. I'd had no difficulty climbing the Rockies eastbound or westbound, keeping up with traffic at 65 mph or so. It was all I could do to maintain 50-55 that day in Oklahoma.

So, I already knew aaaalllllll about wind resistance and its effect on fuel usage. But thank you for the independent confirmation.