It came with some pretty aggressive all season tires.
I have a BIL who owns an older F-250 diesel. He works for Pirelli and can usually get some decent prices on tires from them. Last year he replaced his AT's with some mud tires. He said he lost 2 mpg with the more aggressive tire. May be part of the problem.
I suspect you are probably right. I thought about getting an extra set of rims and tires for summer driving, but the prices on such things are ridiculous and I would never save enough money on gas to justify it.
I do love the truck, though.
