Jon,
Welcome. I've been able to eek out as best as 23 MPG on the highway, no towing, but normally more like 21-22. I have no mods other then the MBRP exhaust, right now. Around town I can get between 18 and 20 MPG, depending on how I drive. Much better then my friends with their gas F-150's. That's why I went with the PSD. By the way, the exhaust didn't change my mileage. Ice