I just got home from a trip from south central Pennsylvania to Illinois and back. I pulled a 6x12 trailer (not enclosed) with a bad boy buggy. Maybe all was 3000lbs. Doing 65 for a little average was around 13 and doing around 74 was right around 11. I think that was terrible for what little weight I was pulling. Should have just taken my 1500 reg cab chevy with a 4.8 V8 in it. It probably would have done that well. Any thought on the bad mileage.

My mpg's have dropped way down...Begining to think its the fuel or something,,,one day its 18 mpgs now doing good to get 15..
I to took a long road trip pulling a yamaha rhino...I was doing good to get 11 to 12..Made me so mad I was tempted to trade to dang thing off...

I was pissed when I saw what I was getting. Maybe it is switching to the winter fuel already. Just thought it would do better. Guess i'm not the only one though.

15 mpg is very average for any of our trucks pulling even a small 6x12 open trailer empty. I used to get 20-21 empty with stock tires, now getting about 18 empty with the 265's. Pulling my 5th wheel(pretty tall) I get about 9mpg loaded heavy or light, dosen't matter. I would slow it down to 65, set the cruise and enjoy your 15mpg. You bought it to haul, not to get mileage!!

I just towed a boat 1500 miles to the keys from N.Y with my 3500 srw and averaged 10.5 going 62-65 mph with a combined weight of 22800 lbs, even empty I only get 16-17 0n the hwy at best, my truck has never seen these great claims to 20 + mpg , your is average, just like mine.

I guess I didn't get one of the good mpg trucks. My buddy has a 07 LBZ an always tells me the great mileage he gets an I can't believe it. He pulls 23 out of his dmax doing 65 on the highway with 285's.

I guess I didn't get one of the good mpg trucks. My buddy has a 07 LBZ an always tells me the great mileage he gets an I can't believe it. He pulls 23 out of his dmax doing 65 on the highway with 285's.

He's lying

He's lying

X2 - Or can't divide... or is trusting a faulty DIC..... or is calculating with incorrect size tires.

When towing, I notice a HUGE difference as my MPH increase. Around 50-55 is the best and it goes down drastically as you get over 60. Easily a few MPGs for every 5 MPHs over 55.

ever clean your maf sensor? when dirty can drop mpg 20% easy

Winter blend fuel will kill your mileage.

were you in T/H mode?

I pulled a 14' flat bottom bass boat in T/H and got my usual light load mileage of 12 MPG. a couple weeks later had a very similar boat ( probably could have been twins ) and ran same roads but this time I left it in NORMAL ( no T/H ) and got 14 MPG. for some loads under a certain weight it seems that T/H can be overkill; this set up was probably under 1000lbs; so not really close to the 3k you have

what I'm sayin is that your mileage is normal for towing

Winter blend fuel will kill your mileage.
I agree, winter fuel will do it. I have seen mine drop in the past couple weeks and from what I read on this forum I think my truck get a little better than average fuel milage.

23 is possible with 285s

1000s of things affect mileage I'm sure your 20s don't help. On cross country trips I have watched my mileage go from 20-16 unloaded.

Do we have winter fuel in Houston?

I know my wheels don't help and I hardly ever use T/H except with something real heavy or to help slow me down. My buddy that told me he got 23 is hand calculated but he is doing 65 on the highway with no load. I have never cleaned my maf sensor. Might have to try that.

For me, speed is the killer in the hunt for good mpg. Also, wind, tire air pressure and hills. In Arizona, I don't notice summer vs winter fuel. There is also a difference when I don't run an additive.
On the DIC, I can get 23 at 65 on a totaly flat highway, but, hand calculated, the DIC is usually 2 mpg high.
When I tow, I run my programer on 3, at 6500 lbs, I get 11-12 at 65. My neighbor with a 6.0, with the same load, gets 7-8. When we left the dunes a couple weeks ago, during a wind storm it was worse, he had no power and his tranny was running hot. My truck ran fine.
As far as, gas vs diesel, you can't get the same performance in towing. I kept having to slow down to wait for him.

Several things:

Big tires, speed, wind, load/hills, highway vs. side roads and winter fuel are all big mpg killers - 1-3mpg loss for each

These are big, heavy and powerful trucks with low gear ratios and automatic transmisions - Claims of over 21mpg with anything but a bone stock truck, empty going 55mph in the summer, all highway driving are not likely to be true.

Brand new bone stock my truck would get 20mpg if I was on the highway more than 80% of the time. Now with 285's, 4" lift, shell, and Hypertech Stage 2 I get 16mpg (summer) pretty consistently. I did have a period where I was down in the 12mpg range on a set of long trips. I discovered the WIF sensor was leaking - slow but sure. To put it in perspective, a gasser with the same setup would be in the 6-7mpg range.

QUOTED: "I just got home from a trip from south central Pennsylvania to Illinois and back. I pulled a 6x12 trailer (not enclosed)..."

Your trailer is not enclosed. If you would've put a tarp over the top, you would've reduced your drag considerbly. Pulling an open box creates a lot of drag.

Do we have winter fuel in Houston?

I don't think so

Claims of over 21mpg with anything but a bone stock truck, empty going 55mph in the summer, all highway driving are not likely to be true.

BS while not overly common some do. With 33s I have gotten 22 with a new tune I'm running at 65MPH. Stock with 33s I could get ~20 occasionally 21 at 70.

Pardon my ignorance but is the maf the regular air filter on our 6.6's? If not how does one clean a maf? :o::o:
As to mileage winter fuel mix here in upstate NY really drops MPG. Winter mileage right now is 16.6 mpg for me. I use to get 20 to 21 mpg hand calculated with a rare 23 mpg, but I could not duplicate it this summer; best I could get was 19.2 driving 60 to 63 mph at 1550 rpm in 6th on turnpike driving. While pulling my fifth, truck and fifth 22,700 lbs combined unit on Cat scale, I averaged 10.3 mpg, hand calculated, average on an 18,530 mile trip to Alaska and back. Hey no complaints there as the truck performed floorlessly over the 15 weeks the trip took.:)

Several things:

Big tires, speed, wind, load/hills, highway vs. side roads and winter fuel are all big mpg killers - 1-3mpg loss for each

These are big, heavy and powerful trucks with low gear ratios and automatic transmisions - Claims of over 21mpg with anything but a bone stock truck, empty going 55mph in the summer, all highway driving are not likely to be true.

Brand new bone stock my truck would get 20mpg if I was on the highway more than 80% of the time. Now with 285's, 4" lift, shell, and Hypertech Stage 2 I get 16mpg (summer) pretty consistently. I did have a period where I was down in the 12mpg range on a set of long trips. I discovered the WIF sensor was leaking - slow but sure. To put it in perspective, a gasser with the same setup would be in the 6-7mpg range.


Using gps and hand calculating mpg, I was able to achieve over 23mpg with BFG 285s.

Granted this was when fuel was $5 a gallon, and I would never go over 68mph.

Now driving 75+ with toyo muds in 295s I just averaged 16-18 on I-40 from CA to Kansas. (need to change air and fuel filters)

I do think winter fuel is being used now, which accounts for a major drop in mpg IMHO.

Several things:

Big tires, speed, wind, load/hills, highway vs. side roads and winter fuel are all big mpg killers - 1-3mpg loss for each

These are big, heavy and powerful trucks with low gear ratios and automatic transmisions - Claims of over 21mpg with anything but a bone stock truck, empty going 55mph in the summer, all highway driving are not likely to be true.

Brand new bone stock my truck would get 20mpg if I was on the highway more than 80% of the time. Now with 285's, 4" lift, shell, and Hypertech Stage 2 I get 16mpg (summer) pretty consistently. I did have a period where I was down in the 12mpg range on a set of long trips. I discovered the WIF sensor was leaking - slow but sure. To put it in perspective, a gasser with the same setup would be in the 6-7mpg range.


22.4MPG at 68 on a bone stock truck and yes it is very repeatable. Under those conditions I never get under 21.5 MPG all hand calculated with the truck filled right to the top of the neck!

I pull a 38 ft 5th wheel 16000 lbs. My duramax will pull that trailer streight up at any speed if you asked it to as long as you can put the fuel in it. 10 MPG, 11, or 12 with a tail wind. I straped a 55 gal aux tank in the back and I can go 8 hours on a full load of fuel. About $180 a day for fuel.

End of September took a trip from Cedar City, Utah to Carson City, Nevada and back (not towing). Averaged about 73 mph round trip with about 40 miles of city driving thrown in. Averaged 19.6 mpg round trip. Did the same trip last June towing a 14x6 enclosed trailer (about 2k lbs) and averaged 16.7 mpg. Truck is totaly stock. Normally get 14.5 to 15.5 mpg around town. I've noticed my milage has dropped 1.5 to 2 mpg around town lately, possibly due to additional warm up time and winter blend fuel.

I drive a Med duty C5500. Its a motor home. Last summer we drove from St. George to the midwest and back via 15-80 and two lanes back to KC thru Kansas, Oklahoma, Texas, New Mexico, Colorado, over 70 (ugh) back to 15 and up to the Ogden area. The whole trip I averaged 8.3 while towing a ford ranger. The best I got on an indvidule tank was 9.9. All fill ups were hand calculated. I was not using an additive at the time. I am now using Stanadyn performance and a mix of twocycle oil. The truck runs quieter and the milage on the last trip from Northern Ut to St. George was 9.4 over mountain and dale. My gross combined at the time was 27K or there abouts. I have the records for the whole summer including what I paid for the fuel. Don't ask. I can't get the grin off my face for the mileage. Oh yes I was trying to maintain 65mph so the average speed was somewhat lower than that. I didn't buy this motor home for the mileage but for the comfort. If it was for mileage it surely would be a wrong choice to go to a motor home. I would be driving my Envoy and staying at a motel.
Max:D

2007 LBZ the best I can get is avg. 14.5 mpg city/hwy unloaded. Pulling my 30 ft Travel Trailer is 10.5 to 11 mpg it weights about 8500 lb. Everthing is stock.

I must of got a good one then with my 07 classic. my DIC actually reads about 1.5 to 1.75 low to what the gps and hand calc say. with the winter fuel here now I dropped from an average 19.7 to 17.3. but when heading across the state empty if i keep it around 73 or 74 I will get 19 to 21. I have got better than that, just had the wind in my favor both ways.

loaded it varies but with all the different trailers i have and pull its 16 to 17 mpg, unless i am in a hurry then it's 14.

that is mostly in the country. when i go to work in seattle for 4 or 5 days at a time i see about 17 in the summer and around 16 now in seattle driving.