Gas might make some difference? I usually run Sunoco or gas from one of the area's larger convenience store chains. Either gives pretty good mileage and has in my last three trucks over the years.
On the other hand, gas from the local Sam's Club station is really pizz poor for mileage. Same experience with the ol' girl's vehicles. She won't use Sam's gas.
Don't think I'd have any problem getting close to 22 MPG highway if my truck didn't have so much weight in it on a regular basis. But I gotta have my stuff along or I feel nekkid and helpless.
Also noticed that mileage dropped a bit when temps were in the teens and low 20s.
