I usually get 22-24 mpg which is better than my gen2, truck has more torque and better pickup. I just wish the tank was the same size so I could go longer between fill ups. I still go the same distance at 340 miles when not loaded down.
I also have a factory spayed bed liner. I like it a lot. Stuff still slides around but it doesn't scratch the bed. I plan on getting the Toyota rubber mat as I had it in my 2Gen but it doesn't fit in the new bed design.