I just towed with mine last weekend(04. 5 Laramie LWB, 4wd, Auto, Q-Cab). I rented a U Haul car carrier & put my '78 Blazer on it. My wife had never been to West Texas so we took off early on Mothers Day. The truck had 700 miles on it when I first hitched up to the trailer & pulled it empty for about 75 miles to get the Blazer from the ranch. I guess the average speed empty was about 50 mph. When we got on I-10 I put the coals to it running the speed limit, 70 mph or thereabouts, to Fort Stockton. It pulled the hills around Kerrville like a freight train running in overdrive. The mileage on that tank was 10. 5. The Blazer sat pretty high pulling a lot of air. Then we went to Marathon & Del Rio. We had a stiff head wind & not much of a run at the hills which were pretty steep. I did put the truck in Tow/Haul mode when we went through little towns on US-90 to keep the rpms up. We refueled in Del Rio & got 9 mpg on that tank. From Del Rio back to the house the road was much flatter & we ran about 65 mph. We unloaded the Blazer & I took the trailer back to the U Haul dealer. The truck still had over half a tank so I waited a couple of days to fill it up again. I used it down to 1/4 a tank. I check the mileage when I filled it up & got 13. 6mpg. I'm on my first tank running empty & see 15. 8 on the overhead with 50/50-city/highway driving. Total towing miles was about 800.