Hi just bought an 07 cc ltz with 30k on it. Unloaded I am getting about 17.5 hand cal on the highway. Just grabbed the boat a pontoon wieghs 1800 lbs no big deal until I checked the mileage 9.9??? I towed the same boat with my 05 d max and would get 14! Heck my step fathers dodge caravan gats 12 towing this thing. I am suppose to go to Utah this fall with about 6k behind it I am worried what I will get! Any ideas? Any fixes? Chevy dealer told me everything was fine with the truck.

Not unless your trailer weighs 12k it isn't.:D

Is this reading through the dash or hand calc? For comparison I went on a 950mile trip from CA to Utah and got 13.2 mpg with an 8k TT. Hopefully just a glitch with your readout.

I have been complaining about the same thing to my dealer ever since the truck was about 6 months old. Before I start, let me say that all MPG figures that I cite are hand calculated.

When the truck was brand new, I used to get up to 22 MPG on the hwy at 60 MPH. The fuel milage has been going down steadily since the truck had about 5000 miles on it. I am currently starting to see a slight increase in fuel milage lately though. The worst milage that I have ever recorded was on a trip from TX to WA while towing my 7000 lb TT. During that trip I was traveling at the full speed limit the whole way and I got an average of 9.9 MPG for the whole trip but I recorded one tankful at 8.6 MPG. That was in Colorado and I was doing the full speed limit of 75, IIRC.

I have read several posts where people claim MPG in the low 20's and I don't believe it. I think that many who claim to be doing a hand clac are in fact using DIC readings, which can be notoriously inaccurate in many cases. I have seen numbers as high as 24 MPG on my DIC and when I stopped to re-fuel and did a hand calc I got in the 17 - 18 MPG range.

I would say that there is one thing that I did that I think may have started to give me better fuel milage as of late and that is I have been accelerating hard from every stop, whether towing or empty. After reading some of the posts on this site I have come to think that I may not have really broken in my engine correctly. I have been driving it light footed ever since I got it and from what I read, that does not break in the engine correctly. Anyway, I have more than 35,000 miles on it now and it may be just starting to be broken in now.

The last trip that I took while towing I actually saw 11.9 MPG for the whole 300+ mile trip. That was while towing my TT over Chinook Pass in WA State and about 30 miles of that was towing off road on USFS roads to a friend's property in the back country. On that same trip that I have taken many times my previous best MPG was just over 10 MPG.

Anyway, one thing that I have learned is that you have to put aside MPG worries and just enjoy the truck. It is a good truck. You may not be getting the MPG that you expected but it may get better with time. I am hoping that my truck is finally getting broke in and that my latest MPG figures are not just a fluke.

I get 16-17 on the hwy unloaded, 12 around town and 7-9 towing my trailer and wheelers, all hand calculated. Towed just two wheelers two weekends ago and was getting 11. Took it to the dealer and as expected they found nothing wrong.

I hand cal. the mpg although the DIC on it has been within .1 or .2 on the tanks I have put in it. I ccan understand 9.9 (DiC had 10.0) if I had a real load on the truck put 1800lbs should not take it from 17 to 9 ????

Maybe I should drive it a little harder then? Who knows???

Here we go again. First of all Armylifer, thank you for your service, my daughter graduates from basic on friday! I am one of those who gets 19 to 20 mpg average unloaded at 65 to 70 mph, and 11+ pulling an 8k TT at 60 to 67 mph. I have checked my dic against hand calc and it is so close I rarely bother to hand calc anymore. Remember, the dic is average mph, when you reset it, over a short run might display 24 mpg. Gee, if I reset it going down a steep grade, it will show 99 mpg! When you check your mileage, you should check it on a long trip; the dpf goes into regeneration approximately once every 450 miles. If you only go on a 100 mile trip and you had one regen, your mileage will be lower than the next 100 mile trip without a regen. On long trips these variations cancel each other out. That being said your mileage indicates something wrong with either your truck or your driving style; I assume it is the former. I will get hate mail for this, but if I were you I would take it to the dealer and have him run a diagonstic check, and maybe reprogram it with the latest factory setting. They can also tell you how many times it has gone into regeneration. It sounds like the previous owner messed with it; that seems to be the cause of most problems IMO.

Garye,

Quick question, how long was your trip with the boat? If it was fairly short you could have experienced a regen which would have squewed the results quite a bit if it wasn't averaged over 200 or 300 miles.

it was about a 140 miles so maybe it had a regen? I did not realize they went into regen that often. I hope that is all it is. Like I said I am new to the LMM and not trying to rehash any old arguements. Just trying to figure out what is going on. As far as the former owner it was a government truck a small town in Miss. was the former owner I doubt they would have changed much on the truck but I do not know. Also I have already had it checked for the latest program changes at the local chevy dealer. I will ask them to check the regen and see when it did the last one.

Thanks again.

If you checked you mileage over that particular 140 miles, it could have been that the regen just happend to accure during that trip. Mine does a regen about every 400 miles. Lots of stop and go with a trailer shortens this dramatically, long runs on the highway with a trailer lengthens it.

Just to throw in my two cents, but there are many factors when mileage is concerned.
As others have said, a Regen could have occurred. When towing and working a truck hard, regens can occur more often then the typical 400 mile range (give or take some miles).
A pontoon boat is one hell of a wind break. That in itself is mileage buster.
Average towing mileage appears to be between 9 and 12 give or take based on driving habits.
I typically average highway in WV around 18 on a trip, in general mixed city/highway that occurs on a daily basis, I get about 15 to 16.
I have driven before on long trips to certain destinations and got 21 miles to a gallon! Doesn't always happen, but does happen on the same trips. My last trip to VA I averaged 17 with 720 miles highway and 300 miles city stop and "race to the next red light". Funny how mustangs try to keep up!
Towing an 18' flatbed with a 3500lb tractor I get 12 miles to the gallon on the highway.
Although the ALlision is smart, it is still possible that it would lug along in a higher gear than desired. Many members on here like to use the manual mode. For each their own, this is not right and it is not wrong, it is a preference, and at times a necessary thing to do if the tranny is constantly shifting at the in between speed.
ALthough you don't like those numbers, it looks as if it typical. 140 miles is really not along range to actually get an accurate measurement in mileage. On the trip I noted where I get 21, I only get 18 for the first 150 miles, it then picks up to 21 (BTW, it just gets to 21 according to the DIC) in the next (last) 100 miles. In the end I have hand calculated the results, and my DIC has been almost perfectly accurate (give or take tenth).
Long winded I know, but I hope it give you some other things to think about.

Hey Oregonnovaguy, congratulations to your daughter. I thank her for her service, and you for supporting her.

Thanks for the help everyone. I am heading to Cullman Ala next weekend with the Jeep on the back of it I will see how it does on that trip.