Same here. Was getting about 40mpg with a roughly 70/30 mix of highway vs. city driving, now I'm getting about 33mpg. Big difference is the AC. Same thing happened on my Fusion hybrid. Winter and summer always got lower gas mileage, but usually only about 4mpg, not the 7+ I've seen on my...
I just bought mine last week from Long McArthur, worth the trip for a good truck at a fair price. It did have a green sticker for some reason, and a lot on the lot do.