fuel mileage w/ Duramax

[bigdob24]

I have a 2006 Chevrolet w/ 6.6 Duramax and Allison Transmission. I am looking at a Sundance 3300 RCB and would like an idea on what to expect with fuel mileage on one of these larger units.
Right now I pull a 19' toyhauler and get anything from 9-12 depending which way the wind is blowing
Any input would be helpful.
Thanks
Dan

 

[sailorand]

Dan
Last year I towed from Palm Springs, Ca. to Vancouver BC. I got 12.2 mpg keeping the speed at 60 mph. Just came from Vancouver to Seaside Or. at 12 mpg.

 

[jimtoo]

Hi Dan,

Welcome to the Heartland Owners Forum and hopefully family.

I moved this post to the Towing Area where you should get plenty answers. Myself, I have an 04 GMC 3500 Dually, D/A and pull a Bighorn 3055RL. I gross about 22,500 loaded and ready for the road. I get about 10.5 to 11.0 .

Jim M

 

[gmc]

I have an 06 duramax and pull a bh 3055 at about 21,300lbs and average between 9.5 and 11mpg. depends on the terrain

 

[bill40]

Hi Dan weclome aboard.
I was getting about what Jim was getting with my 05 (3.73 rear) and the 3500RL. I had the Banks system installed and I know it did help my empty mpg a good bit. Will get a good idea in a week when we leave for a trip. As Butsh said depends on the terrain and which way the wind is blowing, that can be abig deal out west.

 

[Forrest Fetherolf]

06 2500HD Duramax 6 spd Allison extended cab, CGVW 22000+ lbs 3600RL Bighorn = 10.5 to 11.5 mpg @ 62 mph 1650 rpm. Summer blend diesel .5 mpg better than winter blend.

Forrest

 

[bigdob24]

Thanks for all the info, this is a very good site . I have been looking around and there is everything here when ya look.
Thanks again
Dan

 

[Del600]

I have an 06 GMC and tow a Sundance 2998RB, I have yet to get to the scales..... but keeping it under 2000 rpm I see as high as 14mpg, and as low as 10.5.

 

[CrazyScotsman]

A lot will depend on what your rear ends are, 3:73 or 4:10's if 4:10 expect lower fuel mileage than the 3:73's

 

[brickman]

I have an 04 chev e/c s/b gas that I have never gotten better than 8 mpg towing 7800# conv. trailer. Went to 08 GMC (its a rocket) with this Landmark and get 12.5 towing @ 61 mph, and 20 dry @ 71 & 22 @ 60 mph.

 

[htneighbors]

Like others - 10.5 towing the CYCLONE; 20-21 otherwise.

 

[jwb187]

An 05 here, just returned from the Smokies, traveled about 900 miles round trip most of it on I-40 across Tennessee. Tried to hold it to around 63-64 mph to keep from getting run over by the thousands of semis on that road!!! I got exactly 11.0 MPG. jwb.

 

[newbie]

I have an 04 chev e/c s/b gas that I have never gotten better than 8 mpg towing 7800# conv. trailer. Went to 08 GMC (its a rocket) with this Landmark and get 12.5 towing @ 61 mph, and 20 dry @ 71 & 22 @ 60 mph.

Exact same here. And I take it real easy also. Stay 60-65 regardless of higher posted speeds (when towing)

 

[yondering]

'06 duramax

New to this forum, I, also, have a '06 3500,duramax,6 spd allison, pulling an '09 3580RL Bighorn.about 24,000 gross weight. On our last long trip,feb 09>april 09, we towed 9,860 miles, and averaged 12.8 round trip, from Texas to northern California and return. only improvments I have done are K-N Filter system and Bully Dog turbo back exhaust. Good luck, and God Bless ya. Al Weaver, Marshall, Tx

 

[porthole]

I have done a couple of changes to my truck and recently averaged 13.5 for 1800 miles, about a 1/3 of that in the mountains of western NC, GA and TN. That is up from 11.5 previous.

This is with my motorcycle trailer which is a lot lighter then my trailer. But I regularly cruise at 70-75 with it when I can.

Something I just heard about but have not tried yet is towing in 5th (with the tow mode engaged).
This will have the engine run at a slightly higher speed but not work as hard.
Food for thought.

Duane

 

[itsbeertime]

I *used* to get approx 11.5 according to the trip computer. I recently upgraded my OEM 245 tires to 265's and according to the trip computer I have lost 1.5 to 2 mpg. Not sure how that works, but it sure stinks.

 

[ct0218]

With the Duramax/Allison combination you cannot change the computer to compensate for the size change. GM cannot do it, and many dealerships will not even work on the truck if your problem relates to drivtrain or mileage problems. That said, putting a larger tire on would make you believe that with the larger circumference you would get slightly better MPG--but, the opposite happens. It has been discussed many, many times on different forums that the additional mass and weight actually reduces your MPG, and changes your rear ratio to a numerically lower number. That means that it will hurt your towing because your ratio changes from 3.73 to something in the 3.5X to 3.6X range. Even though the tires look small on the GM 2500/3500 series they are the right size for MPG and power through 2006 or 2007 model years. At that point thet did change the Allison and Duramax computers for a slightly larger tire and wheel. Unfortunately, none of that is backwards compatible for those of us with the older models. The newer trucks do not get as good mileage as the older do even though they have a 2nd overdrive, possibly due to the size change, and definitely due to the DPF.

 

[JohnDar]

With my '09, I got about 11 mpg when I towed our BH up here to Indian River. At that time, it only had about 3000 miles on it and I kept it to 65 mph. Driving up here today, without the trailer, I was getting 18.4 mpg until I hit the hills north of West Branch. Then it dropped to 17.0. I was cruising at 75 mph. Truck only has about 4200 miles on it so far, so it is far from being broken in.

 

[ct0218]

I have heard many say 20K miles for the breakin, and whatever mileage you get at that point is it. I have 148K on mine now and has been consistant for a long time. Changing the speed from 65 to 70 drops my mileage about 1.5 to 2 MPG.

 

[Bob&Patty]

Clark, could you clear something up for me please. You say in your post that if I change tire size that I can not reprogram the trucks computors. Also can you tell me who has said this. Was it a Chevy dealer or someone on a forum. Dont want to start a fight here, but I work as a Chevy tech. When I changed tire size to the 265's, I installed the GM scan tool and reprogramed mine. My speedo is right on the money, trans shifts at the right shift points, and my ABS works as designed. Thanks in advance for your input on this issue. Bob