I’ve noticed that on our N* (the same one as Ardvark has) wind is THE determining factor with mileage drop or gain.
On the way to Quartzsite, and after gassing up at Pahrump NV we got a pretty good tailwind and it was slightly downhill. After 121 miles the lie-o-meter on the truck said 17 mpg. For a 10K pound, loaded truck camper? The proof in the pudding was on the return leg of the trip where we had a headwind and it was slightly uphill.
11.1 mpg. Our usual overall average is 12.6 mpg.
I just don’t know how you could isolate or even measure the causative effect of wind or vertical center of gravity besides mpg.
jefe de nada
2020 Ford F-350 XLT FX4 4WD SRW SB SC 7.3L Godzilla Gas TorqShift 10R140 397 amps dual Alt dual batts Frnt Dana 60; Rr Dana M275 E-locker 4.30's 4580/4320/4066# payload 7243# curb wt. 11,300# GVWR 5-er prepped. 2020 Northstar Laredo SC, 12v compressor fridge, cassette, 320w Solar sub zero insulation.