I have a new truck (stock), 3500 miles so far.
Haven't seen more than 13 MPG around town, about the same on a trip pulling a 8K TT. I have a fairly heavy foot, but come one, shouldn't it be better??

do a search for mpg or mileage.. you will find more than enough threads on it. It seems to be common for the new LLY's to drop in mpg shortly after purchase, but they do get better with each tank.

I have 5800 miles on my 05 LLY 2500, and that's is the same mpg on my last tank, I here from reading other replys form the forum it will get better around 10,000 miles. It would be nice if the price of diesel would come down to what it was a year ago ($1.45 in my area) now $1.95-2.20 !!

I have 11,000 on mine now and get13.5 in town and about the same pulling 6500 lbs, 18 on the highway...2500HD, 4x4, CC, SB. It hasn't changed a lick since I bought it. But to me this is awesome. My old 95 C3500, CC, SRW with 454 got 9 in town, 12 on the highway and 6.5 pulling the same trailer. I keep hearing when you get to 5,000 or 6,000 or 10,000 you'll see and improvement. Never have seen it. Although I will be towing for the first time since hitting 10,000 today so maybe, but I don't expect it. I guess it is just a matter of perspective. Sure I would love to get better fuel mileage, especially at todays prices. But to me, coming from the 454 I think the mileage is awesome...especially when I look at what it will do.

i have a 04.5 2500 with a 6inch lift, 20inch wheels and 35's i get about 12.0 MPG

i only have about 7k on the truck

As many have noted, I also noticed an improvement after 10K miles. After owning the truck for a year, I have come to the conclusion that a heavy foot and speed (over 65) will kill mileage very fast. With my camper loaded, I only got 9mpg @75mph against a 30mph headwind on I90 in SD. On the same trip, I got 14mpg crossing the Rocky Mountain National Park (12,000 ft) road at 35-45mph!

What are your driving habits in town? These are very heavy trucks and it takes a lot of fuel to get them moving. If you are having fun with the new truck, and stomping it from light to light, the mileage will drop like a rock. Also, heavy stop and go traffic kills fuel mileage.

If you are driving it conservatively in town and timing most of the lights, then you should be getting around 16 MPG. The 13 mpg on the highway with a full size conventional 8K travel trailer at 65 MPH sounds about right.

4200 miles, best 17.12 empty. Worst was bucking 40mph winds pulling a 28ft travel trailer about 9mpg. Avg is about 15.5 empty highway and 11 loaded highway. But heck its only a week old!!:ro)

Slower you go, the better it gets over long distance, the moment you encounter stop and go traffic, it goes to the crapper. If you do LONG stretches of highway/freeway, then you'll get some pretty decent mileage, as long as you keep it under 70mph or 2500rpm.

19 mpg on my last trip at 75 mph with some stop and go. anywhere between 13-17 in town. and I have a heavy foot. I noticed a big jump after I straight piped it. and a lil bit more when I put the power pup on.

Your MPG is pretty normal. Around town mileage stinks for above mentioned reasons. I get over 20mpg at around 60 mph empty. I am 8900 miles into a trip with a 5000 lb travel trailer. 12-13 mpg. (which I am happy with). Total trip is 13.5 mpg with about 10% of distance empty. If it is flat and you have to tow under 50 mph, don't use the tow/haul if you have a lighter trailer. Ruins mileage cruising in 4th gear. I believe this truck is designed with best MPG being worked in a rural highway environment. Really needs a 6th gear for high speed empty cruising. Might help if engine was de-tuned a bit and smaller displacement. The heavy weight and engine/trannie characteristics really make for a safe tow vehicle compared to others I have had. Want bad mileage? Try driving it on a rough two-track real slow

Went on 1900 mile trip pulling a 9000lb v-nose snowmobile trailer from Iowa to Wyoming and back. I was only getting 5-8 but we were going pretty hard (75-85) and I had the 40 pred. tune in and 285 75r 16 tires. Now with about 2500 miles on I'm getting 15 with mix between town and highway. I have had the 65-85 and 100 tunes in briefly for very short (0-60) spurts ):h during the last tank and I can't seem to keep my foot out of the throttle :help: with the 40 in so I'm happy with the no-towing milage. My 02 6.0 with exhaust, K&N and Hypertec would pull 11-12 with this type of driving. If I can get 3-5 better than it I will be pleased.