Originally Posted by AlariWild
I just got a ROO23IKSS and I am seeing this when towing...
2006 F150 4door 5.4l V8 @ 63mph and 1800 rpm in Overdrive gets about 9mpg in Florida.
I later found out that my hitch was totally not setup right and the dealer never emptied the 36 gallons of fresh water.
I too have a 2006 F150 5.4L, but a Super Cab. Final drive ratio is 3.73. The Roo listed is about 800 lbs. heavier than my trailer (Surveyor 283), but about 4' shorter. Comparably, then should tow similarly. I used to typically get 10.5 mpg or better while traveling on fairly level ground.
The water in the tank should not be a biggie, unless you are doing a lot of stop and go traffic, or hills. It might make a slight difference in tire friction against the road.
On level ground, I like to pull in OD, as the fuel mileage is better than locking out of OD. I usually do not use cruise control. The problem is, we don't have level ground in this part of Virginia. I like traveling in the Tidewater area because of the increased fuel mileage.
Several factors can contribute to my fuel mileage. The wind is a biggie. I went across the Chesapeake Bay Bridge Tunnel 1 time with a headwind, and my truck would not stay in overdrive......and that is about as flat as flat can be. I have a low profile trailer, with a fairly steep front end rake that I contribute to decent fuel mileage.
Tires: I switched my OEM tires out last year for a size bigger and a bit more aggressive tread, and I don't get the mileage that I used to. I am usually still over 10 mpg in the rolling hills around here, but not as good as it was before the tire change.
Final Drive ratio. Not sure what you have, but 3.73s seem to work good for me. A higher ratio (3.55 or 3.23) might not allow the engine to rev into the "sweet spot". Usually lower revs mean better fuel mileage, but the engine may be working harder.