I have one of the new F-150 pickup trucks with the twin-turbo V-6 engines, also called the Ecoboost. Traded a 2003 Ranger FX4 for it, and have been very happy with the fuel economy. I'm not a hypermiler at all, and have been consistently getting 17.4 MPG on rolling terrain at 70, and 19.5 MPG on flat level ground at 70. It goes over 20 at 65 MPH on flat ground, but I've never found more than 4 or 5 miles of it to really try it out.
The few times I've been on a road with a 55 MPH speed limit, it definitely goes well into the 20's somewhere
The HIGHEST I ever got the Ranger was 17 MPG at 65 MPH on flat, level ground in Illinois for about a hundred miles.
If you're wondering how I found this place since fuel economy + pickup truck is usually not mentioned in the same paragraph, I was trying to figure out what on earth the pickup had an air dam for. Never seen one of those before lol
After what I've read here, looks like I should leave it on unless I just want to buy more fuel for no reason