Just returned from a 2,600 mile round-trip from SW Wyoming to the Northern California coast, and back, with a few "side trips" between Eureka and Redding on some pretty twisty up-and-down two-laners through the coast ranges. (Hwys 3 and 299 for those that know it)
Truck usually gets about 15 mpg. on such a trip, which includes lots of miles on the interstate at a constant 74-77 mph. (posted speed limit is 75!) On this trip, the average for the entire thing was 11.2.
On the interstate legs, pegged at 77 mph, often kicking out of overdrive, it dropped to a dismal 10.3. OUCH!
I did keep it moving right along though, especially up the hills. The "test" stretch was from Salt Lake City to Reno on the dreaded I-80. There was no wind either way that was any factor. So, a 5 mpg drop, 33 percent.
Mileage was suprisingly better on the two-laners at slower speeds, even though they were up and down hills and winding roads. Off-interstate mileage was 12.5 mpg. The best, of course, were the straighter flatter roads of the pacific coast (hwy 101, etc.) Got 13.6 on a tank there. So, it appears overall speed was more of an influence on mileage than terrain or varying speeds. So, if one slowed down to 65, or even 55, mileage would be only very little affected. At 77, it just sucked the gas.
As for the comfort level, most of the time I never even knew the trailer was back there with my F-150 and the V-8. The trailer towed easily, even with some mild cross winds of 15-25 at times along the coast ranges and in western Nevada (non-interstate). It never affected my speed on any road, and the load stayed secure throughout the trip.
On a longer trip with lots of driving like this, I'm very glad I have a 6x12 rather than a 7x14.
So, "maybe" air tabs will be in order for high speed interstate driving.
I'm not sure if its air drag, or just the increased towing load weight that drops the mileage so bad at higher speeds.
In other trip news . . .
Temperatures at night were int he 30's and low 40's where we camped, and we were snowed on one night near the Trinity River at Weaverville. However, we slept warm as planned, and the little Coleman heater did its job in the mornings and evenings. The little 12-volt heated pad for the bed was awesome for pre-heating. Won't ever leave home without it.
I caught some steelhead on the Eel and Trinity rivers too!
(I won't be able to make the summer get-together due to my work schedule) Will likely camp along the Trinity, Redwood Cr., Van Duzen, and Smith rivers. It will be one of those "wait and see when I get there" sort of schedules, depending on river condiditions and where I'll be fishing.
