I took a four day, three night trip two weeks ago. Open highways, little to no traffic. Hilly to mountainous. I kept speeds between 55-60 on straight portions in valleys because my wife and I were in no hurry. Averaged 21.7 until the last 175 miles, pushing a strong headwind at legal 80 mph over the interstate. Dropped my overall mileage for the trip to 20.8.
Otherwise, 17-19 for day to day driving.
I run BFG All Terrain T/A KO2’s in stock size, but load range E, so they’re a heavy tire as well.I have BF Goodrich KM3's, which I imagine will hurt my mileage, but they are stock size, so maybe not too badly.
with my BFG ko2's i get like 14mpg