I was wondering what some other people are getting for mileage when towing loads. I get around 16-18 combined and 20-22 highway but when I hook up to my 5th wheel [10,000#] it drops way down to 10-12. I use to have a dodge and it would tow and get 17-18. What keeps the duramax from getting better mileage? I've tried running in all rpm rangers 1600-1800 ok for flat country but lugs to much in hilly country. 2000-2300 rpm runs great but can't run that fast all the time. Really hurts the pocket book when traveling 1000 miles.

About the same as ours...with our enclosed car trailers, they catch a LOT of wind...the small tag is around 10K loaded, while our goose is around 18k loaded...we get around 8/10mpg towing, respectively.

12 ain't too bad. 10 sounds a tad low. I pull about the same fifth wheel and consider an honest 12 OK. Just got the Attitude for my Juice, adjust on the fly and set the tire size so now I can get a little more accurate.

Yep, that's the range I also get. A lot of it depends on the wind. Just this last weekend, with it being very calm, got 12.1 mpg on one leg and 12.2 mpg on another. On the way back with it being quite windy the DIC is showing 9.9 mpg for the last leg so probably 9 mpg when I finally fill up the truck.

Edit:

Oh, and those numbers are uncorrected for the tires. I'm running 265 LRE on the OEM rims.

thats about right. A pull trailer seems to drop mileage to 10 or so. I think the fivers do better since the air stays up after the truck where as with a pull trailer it drops behind the truck then hits the trailer. I also doubt anyone that says they get 17-18 with a dodge while towing. I know people with dodges and the get about the same as me towing the same loads.

x2 on the dodge thing i get the same pulling 15K with my dmax as i got with all my other trucks that were dodges witch is 10 mpg

I see the same thing with my Powertroke, the Dmax, and the neighbors Dodge. Haul a big load or just your hat and the dog, goes down to 10-12. I might do better on the days I exhibit some PATIENCE and slow down; this is a seldom occurance!!

Most of it is wind!

With my 28ft race trailer, 10K loaded and about 6K empty I get the same MPG towing it. This tells me that it isn't the weight it's the drag imposed by the wind.

Also, if I follow an 18 wheeler (at a safe distance) I'll pick up 2 mpg as well.

I just got 12+ towing the trailer last weekend, running 75ish. At 65 it would have been better.

I got an 02 LB7 in my Yukon XL and I just towed a 30' toy hauler(12,000#) from Idaho to Florida. We got 8mpg!!! Every tank for 2700 miles, fluctuated from 7.6 to 9.2, average 8.2. I tried 65 for whole tanks, 70 for whole tanks, following trucks(even very close), no change. Same in the mountains as in the flat planes. Head wind did make a difference. I used Power Service every tank. Normaly get 12-13 in town and have never been on the freeway with out a trailer but i did get 17 once with a 6x12 uhaul trainer in central Utah. So.....10-12 towing looks really good to me.

BB: you still liking the Dmax/Sub combo? Anything you'd do different?? I can't seem to sell my wife on the idea...but I'm trying! LOL!!

I love to drive it and we can tow a 12,000lb trailer accross the US. Next time I will use an 03 or newer suburban/yukon and a 05-06 lbz. Otherwise I wouldn't change a thing(except the fuel economy thing).