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Old 08-03-2015, 11:45 AM   #29
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2012 27' FB Eddie Bauer
Laguna Niguel , California
Join Date: Jun 2011
Posts: 17
We have a 2007 GMC 2500 HD 4X4 (LBZ) DuramaX Allison 6 speed extended cab short bed with the BANKS (Big Hoss Bundle). Never had any issues except one time EGR replace after 100K miles. We tow an Airstream 27ft Edie Bauer. -- MPG's towing at 60 mph around 13-14 miles per gallon. MPG's not towing about 18 mpg @ 65 mph - any faster the MPG's diminish . It's a ROCKET with the BANKS performance enhancement . Next upgrade will be a Banks exhaust brake for steep downhill slowing to save on truck & trailer brake pads. The trailer tow function on the Allison trans over - revs the engine on steep downhills I LOVE MY TRUCK !!

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Old 08-03-2015, 12:21 PM   #30
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1972 31' Sovereign
High Springs , Florida
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2003 Extended Cab, short bed, 140K miles. Average 18 MPG "country" driving, and around 15 mpg pulling the Airstream. Bought truck new, replaced both front wheel bearings at around 65K, rear u-joint at 110K, and just put new shocks, brake pads and rotors on front at 140K. 3rd set of tires due for replacement soon.

2003 GMC 2500HD 4X4 D/A Ext. Cab
Propane Powered Honda EU2000i
Lots of Hot Sauce!
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WBCCI 1350
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Old 08-03-2015, 02:18 PM   #31
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1999 34' Excella
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Round Rock , Texas
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Pre-DEF trucks seem to do better.... Deleted DEF also seems to perform far better.
Peace and Blessings..
WBCCI# 30676
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Old 08-03-2015, 03:04 PM   #32
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2012 27' FB Classic
Jamestown , Rhode Island
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We have 2009 LTZ, towing a 27 ft Classic. With over 15,000 miles of travel, our avg. MPG is 12.5 I would not trade this truck for anything but a new one. Only 64,500 miles and the dealer wants it every time its in for service.
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Old 08-03-2015, 10:37 PM   #33
2008 30' Classic
Orland Park , Illinois
Join Date: Jan 2014
Posts: 20
Great Mileage

2013 2500HD LTZ Duramax w/ ALL the bells and whistles, crew cab, short bed.
13.5 MPG towing a 2008 30' Classic Limited, 65 MPH and 22.5 MPG unhitched!
22,000 trouble free miles. LOVE IT!
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Old 08-04-2015, 04:14 AM   #34
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2012 27' Flying Cloud
W , New England
Join Date: Oct 2012
Posts: 4,678
Originally Posted by flyerboy View Post
2013 2500HD LTZ Duramax w/ ALL the bells and whistles, crew cab, short bed.

13.5 MPG towing a 2008 30' Classic Limited, 65 MPH and 22.5 MPG unhitched!

22,000 trouble free miles. LOVE IT!

I have the same exact truck. Avg 15.2 mpg over 40k miles, at least half of that trailering. How the heck are you getting 22.5 unhitched????
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Old 08-04-2015, 05:00 AM   #35
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Corpus Christi , Texas
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Help w Duramax diesel plz?

Originally Posted by SteveSueMac View Post
I have the same exact truck. Avg 15.2 mpg over 40k miles, at least half of that trailering. How the heck are you getting 22.5 unhitched????

(Time killing this morning)

Record-keeping is usually spotty. Someone using an app like Fuelly or a paper log of all fuel burned is the better source.

To make comparisons about mpg, one must, in order of importance, find:

Details of truck specification (not just 4WD versus 2WD, SRW vs. DRW, or auto versus manual, but tire type and tread design. Aero helpers. Etc)



Driver input (motivation towards fuel economy such as constant use of cruise control; travel set speed; extent of idling, and so forth).

Comparisons are never as simple as they might appear. TT design plus weight and length also apply.

FWIW, I searched extensively when I bought my rig using the above. What I found was that, in the South Central US, with aero aluminum trailers of 28-35' and weighing from about 7-11k lbs, and at speeds under 65-mph, that early HPCR Dodge Cummins were averaging from 14-16/mpg.

This accorded with my experience, overall. I fell within a "normal range", in other words. FE was and is an important consideration for me. Truck spec and truck use.

The weak spots to first consider is ones habits just ahead of truck details. Control for travel speed solo and towing, and things like tire tread design, etc.

In highway solo driving I was at the high end at 24-27/mpg. Where 2WD, SRW and manual trans shone. Travel speed on CC was 58-mph (slower than towing mpg above. I have since changed that). Next to no idle time. Minimization of accel and brake events as well as next to no lane changes. Trip planning and discipline.

So my overall average (50/50 town/country) over the past 55k miles is 21.36. At an average speed of 40-mph (engine run time into miles over a given distance). Towing is now 15-17/mpg in this part of the country.

In short, where, what and whom? (part of country, and at what speed; with how owner spec'd truck). That's the minimum for a comparison.

As a final example: those who have radical changes in travel speed between solo and towing are usually those with the worst fuel economy.

15-mpg annual average is about right for CTD contemporary to mine where 4WD/auto plus tires with open shoulder tread is the norm. From reports across most of the country. I'm an outlier. So would someone living well up into the Rockies. Or northern Alberta. Etc.

SteveSM, what is the percentage drop you're seeing from solo to towing (preferably where truck load is similar)?

40% is the norm for all vehicles, where up to 50% for a gasser pulling a box is that range; and down to --even below -- 30% is possible with a small turbo diesel pulling a smaller A/S.

Test your truck/trailer against the Cat Scale solo weight from when you did WD setup. Approximate the loading with sand, iron or other. A 200-mile loop back to same pump at same filling station. Cruise control, at towing speed.

Think of this as your adjusted highway mpg (as with finding adjusted empty weight being different than published ship weight where driver, full fuel and permanent gear are aboard), as percentage drop is the number that tells the most about the rig and its relationships.

That done, you'll have accounted for problems currently unaddressed, and can then make more accurate comparisons as to something seemingly as simple as solo mpg.

Towing highlights the problems. With turbodiesel pickups (and after tread design) it is CAC system leaks, brake drag, steering slop, and alignment. Second order is engine tune (emissions, usually). Finally are emissions deletes.

A truck with tuning for DEF ought to be seeing 22-mpg at or below 65 given stock tires, ride height, less than a thousand pounds aboard, and lie idle time. Unless GM is truly inferior in this.
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411
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Old 08-04-2015, 09:32 AM   #36
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1986 32' Excella
St. Petersburg , Florida
Join Date: Mar 2010
Posts: 8
Help with Duramax diesel plz.

I have a '08 Chevy LTZ 3500HD LMM crew cab 4X4 with the Duramax/Allison, and we pull "Stella" '86 32' Excella. Love the
truck, "Clyde". We always got, with the factory setup 11.5 towing and
14 city 15 empty for the first 80K. Installed a Motor-Ops 5 stage tuner
from Canada, plus removed particulate filter and other smog goodies.
Went with a Magnaflow 5" exhaust from the block back, and a AiRaid
cold air system. He runs like a bear now.. 14.5 towing-17 city and 19
empty. Clyde was Dyno'ed at 565hp /900+torque in stage 5. Installed a ARE cap with safari racks from windshield to rear lid. Clyde has 94K and
is running great. Our last truck was a '03 Chevy 2500HD short bed, the long bed is great for trips and towing. Added extra fuel and oil filters and only use Mobil 1 every 3 months. Safe Travels Steve
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Old 08-04-2015, 10:19 AM   #37
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2012 27' Flying Cloud
W , New England
Join Date: Oct 2012
Posts: 4,678
Slow - that's a lot more data than I've thought about. Will have to start doing some pen/paper tracking and get away from this confounded digital dashboard.

As a side note - speaking about digital dashboards - why not put the Nav system where the (useless) speedo is? I don't need all that real estate to tell me I'm doing 60 mph and my engine's reving at 1500. Tiny digital readout for those on the bottom corner of a huge Nav screen would be much better!

Back to our regularly scheduled discussion....
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Old 08-04-2015, 10:38 PM   #38
2008 30' Classic
Orland Park , Illinois
Join Date: Jan 2014
Posts: 20

I get 22.5MPG when I'm not pulling on a flat, long (300+ miles), straight length of highway with little or no traffic, going 65MPH with the cruise control on, all 4 tires at EXACTLY 60PSI front tires and 70PSI rear tires, at sea level (600'-700').
If you tickle the speed any up or down, you see in about 10-20 miles the mileage drop a tenth or so and if you go back to 65MPH it goes right back in about 10-20 miles to 22.5. My buddy gets 23-24MPG at times under optimum conditions. I have the 18" wheels with the Michelin LTX M/S2 tires. He had the 20" with the infamous Goodyears that have a less than stellar record in all categories. He just switched to Michelins after a tread separation in only 17,000 miles on the Goodyears.

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