Finally got my final two runs with a 6x12 trailer in last night. All runs with the hatch in the up position, 33% upper grill block, rear wheel skirts removed, standard bed load of 250lbs (tools). Speed set to 60mph fer the first one and 55mph fer the last one. No measurements of tongue weight, rear end drop, or trailer weight was observed.
Run #1 at 60mph yielded an indicated 15.1mpg with an empty trailer, day drive right before rush hour traffic from College Station to Houston, some stop and go traffic near Houston, light rain. Return trip with a fully loaded trailer yielded an indicated 15.9mpg, night drive after evening rush hour traffic from Houston to College Station, light rain. Actual mileage after refueling yielded 16.1mpg.
Run #2 at 55mph yielded an indicated 17.3mpg with an empty trailer, night drive from College Station to Houston, clear skies. Return trip with a lightly loaded trailer (about 300lbs of cargo) yielded an indicated 18.1mpg. After I return the trailer and refuel, I'll post the final mpg numbers.
I'm finding it interesting that as I travel up to higher elevation, my mileage seems to be better than traveling down to lower elevation. Shouldn't it be the other way around?