I've got a '12 Express that had almost exactly the same mileage as yours before a 600+ mile trip last weekend. Mine is 2WD with 3:55 gears. I drove 73 mph on the 70 mph sections and only slowed to 65 and 70 in 2 or 3 places...mostly interstate with a few backcountry roads. I got 19.5 mpg and was quite happy with that. I'm running the stock 20's, and the only mods are a Borla 19" muffler...like a Magnaflow...and a DIY dual inlet airbox w/K&N filter. I used 86 octane winter blend fuel for the whole trip. I don't have EVIC and mileage was calculated the old fashioned way.
I know just having 4WD will affect mileage to some degree, but 5 mpg does sound a bit much. I see many folks on the site mention that the more you go over 70 mph, the worse the mileage gets. Maybe things go to pot at 75 and above.
I know just having 4WD will affect mileage to some degree, but 5 mpg does sound a bit much. I see many folks on the site mention that the more you go over 70 mph, the worse the mileage gets. Maybe things go to pot at 75 and above.
