I just bought a 2015 F150 XLT Sport with the 3.5 EB, 3:31, SuperCab, 6.5' bed in January. I haven't towed with it yet but just went on a 1200 mile road trip from Salem OR to Reno on a mix of freeway and 2 lane roads and about 12 mountain passes. Truck rides real smooth and I didn't feel like I had been beat to death on the road. I averaged 21mpg. I was just cruising around the speed limit so I'm okay with the mpg. Truck weighs 5100lbs with a soft cover, and running boards. The payload from the sticker inside the drivers door is 2030. The Lariat I looked at had a payload of 1956. I cared more about the payload while I was shopping. I knew all the half ton trucks would pull my trailer. The Ram I looked at with a 5.7 HEMI only had 1399 payload according to the sticker which was not enough for my comfort. It did drive nice.
The first tow will be next weekend when I take the trailer to be dewinterized. I had a Chevy with the 5.3 before and got 25mpg on one freeway trip (not towing) and about 11-13 towing on the flats. GVWR of my trailer is about 6500lbs but I'm usually around 5000 for camping.
I personally don't really care what mpg I get when I'm towing because I'm going camping! I don't expect to get great gas mileage dragging a big box down the road.
I really like the Ford and will report back after my first camping trip. Which will be all freeway and 4 small mountain passes.
2015 F150 XLT Sport 4WD 3.5L EB
2014 Freedom Express 246RKS