My trailer is 33' and 7500-8000lbs loaded. I have averaged a best of 10.6mpg and a low of 9.7mpg depending on terrain and headwinds. I always have the cruise set between 60-65mph. I'm never in a rush, I like to relax and enjoy the scenery. Half of the fun for me is getting to our destination!

 

I also found I got better mileage not using sixth gear and no shifting this put my rpms a little over 2000 closer to the good torque numbers the Eco is noted for!

 

Ah yes, the joys of towing. But in the Ecoboost's defence, that is very close to the GVWR with that load. Speed kills mileage even when unloaded. My truck saw 15.3 mpg doing 75mph unloaded, through the mountains of Montana driving to california a few weeks ago. If you want at least 10mpg towing, back it off to 60-65mph.

 

It has more to do with the RPM's than the speed. The Ecoboost has max torque around 2500-2700 RPM, so if you travel in that RPM range, your fuel economy will be better. If your at higher RPM's, you are more into the HP range of the motors RPM and your turbo boost is greater meaning less MPG, or KPG in your case.

I have towed a ton of miles with F-150's, and 70-75 MPH on an interstate is nothing. Capable, confident, and stable. Drove with a friend who purchased a similar camper to what I have in Kansas 2 weeks ago and his 2012 Chevy felt like towing with a Ford Ranger. Squishy and all over the road. We even stopped and made sure air pressure was higher in his tires. I took him for a ride in my truck with my camper that weighs just a bit more than his and he thinks he has an issue with his camper. So I hooked up to his camper and let him drive and now he's mad at me. I want to do a side by side towing comparo on video, but he's getting his bowtie feelings all hurt about it and won't do it. LOL