2013 F-150 (and i've got it all tuned up around town like a WRX). even on slightly bigger tires I can easily do 15 in down and 19 when truly "on the highway". If you drive it like you stole it, then you're going to get 13-14mpg and towing is about the same because you have to drive in boost all the time. It sounds terrible compared to the unloaded highway milage, but its not really any worse than what the 5.0 guys get while towing either.
Ecoboost means either eco OR boost, you can't have a 3.5L engine and expect 7L power out of it unless you're putting 7L gas amounts into it at 2x boost pressure. Because its a flying brick, there is actually a significant decrease in highway milage with speed too. At 65mph cruise control it requires no boost to maintain speed, at 70 it starts having to use boost but not much, by 75 its running 3psi, and by 80 its up to like 6psi in my experience, that just kills the gas milage.
All in all though I love mine, despite some hickups ford has had with it along the way. There are some gotchyas to look out for if you're buying a early year model used, but they've got it all ironed out in the newest generations it seems.