While following the recent thread on swapping 26 gallon fuel tanks for 36 gallon tanks on 2011 Ecoboosts, some trailer towing Eco owners reported 8 mpg and 10 mpg as a motivating factor for a 36 gallon gas tank. I can't argue with that logic.

My question is, when you are getting such poor mileage from a truck/engine combination that is rated at 23 mpg highway, aren't you overloading the engine? It seems like a 5.0L or 6.0L V-8 (or maybe a F-250 diesel) would be a better choice for such heavy hauling. Even though you wouldn't enjoy the 23 mpg highway of an empty Ecoboost, you would probably do better than 8 to 10 mpg hauling heavy loads.

 

I dont have an eco but I have the 5.0 for a little over 2 weeks now and am very disappointed only getting 15 mpg with no hauling at all and about 50 / 50 city vs highway driving. I certainly hoped for better than that when I traded in my 2003 F150, which got roughly the same pretty sad that a truck 8 years newer with 165000 miles less on it gets the same mpg.

 

It seems like every truck towing a travel trailer - diesel or not, turbo, 6 cylinder, 8 cylinder; will get somewhere between 8-12mpg at 60-70mph.
I think it's because you are towing that huge sail behind you. Punching that kind of a hole in the air, continuously needs energy ....

 

My experience with my 2010 with 5.4L engine was 14 mpg when I first got it. After about 5,000 miles the mileage improved, but not much. Now I get about 15 mpg with 50/50 city vs. highway driving and I have driven the truck 15,000 miles. It's not much to look forward to, but it might help ease your disappointment just a little bit.

 

What rear-end gears do you have? Your new truck need a few more break-in miles before you can expect the fuel mileage to improve. Other than that, driving habits, keeping the tires inflated will have a lot of affect on fuel mileage.

 

The engine is not overloaded unless you see oil or coolant temps get up into the red zone. Modern pickups are designed to work hard, and working hard won't hurt them as long as you don't overheat anything.

Towing a big box such as my 7x14 cargo trailer is going to kill the MPG on any tow vehicle. Aerodynamic drag is the big factor, plus whatever weight is in the trailer. If you don't have a heavy enough trailer to get up close to the GCWR of the pickup, then variations of weight in the trailer won't affect MPG very much. On a recent 2,000-mile trip, with empty trailer and grossing 6,700 or loaded trailer and grossing 8,980 didn't make any difference to MPG.

I had a '99.5 F-250 diesel for over 11 years. It was tuned to the 99s and had performance exhaust and intake. Here's my MPG with that rig dragging a 12' high 5er and grossing 16,000 pounds:

62 MPH - 1800 RPM = 12 MPG
66 MPH = 1,900 RPM = 11 MPG
70 MPH - 2,000 RPM = 10 MPG
74 MPH - 2150 RPM = 8.5 to 9 MPG

For the last few months I've been getting by with a 2003 F-150 4.6L, stock. Dragging my 7x14 cargo trailer at 65 MPH it also gets about 10 MPG. Speed up to 70 and the MPG drops to 8.5 to 9. About 200 miles is the max between fillups.

Both those trucks got around 14 to 15 MPG unloaded and cruising at 73 MPH.

I'm expecting my 2012 EcoBoost to get about 10 MPG towing the cargo trailer at 65 MPH, and get closer to 20 MPG when unloaded and cruising at 73 MPH. We'll see.