# Diesel Fuel Mileage



## Steve McNeil (Aug 30, 2004)

I am wondering when the fuel mileage increases on the duramax. I bought a 2006 GMC 2500 back in August. I have approximently 7700 miles on it. I towed my 28 RSS approx. 900 miles round trip this past weekend, mainly flat lands with a few big inclines. I am getting 14 mpg in town/highway (mixed-normal daily driving). I was only getting 10.6 mpg while towing this weekend. I had people tell me that their diesel trucks are getting 20 mpg on the highway and 14 mpg while towing. My friend just bought a used 2006 Dodge 2500 Diesel with appprox. 16,000 miles on it and was getting 14 mpg on our trip. What is the secret in better mpg on these diesels?

Thanks Steve


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## ARzark (Aug 9, 2005)

I have around 17K on my Dodge and just pulled the Outback 2,000 miles. 
This trip I noticed improved mileage (12+ consistently) even through the mountains of ID and WY. The truck felt a little more responsive towing this trip too, not as "tight" if you will. I think it's finally breaking in.

Hang in there, you have a few miles to put on but you should see an improvement. Some say at around the 20K mark it's most noticeable. We'll see.
Good luck!


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## johnp (Mar 15, 2004)

Its going to take me about four years at that rate to break mine in. I was getting between 12 and 14mpg on the first trip this weekend. Didn't have time to put the 500 mile breakin on it.

John


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## Fire44 (Mar 6, 2005)

I drive mine about 10 mins to work each day and average about 14 mpg. We went to Fla in March and got around 20 mpg on I95 running around 70 mph. I have just about 15K miles on it now. I did see a improvement around 10k miles.

My brother in law pulls a Couger 5th wheel and gets around 14 mpg towing. I also have used Stadyne Fuel Treatment and I have gotten about another 1-2 mpg.

Gary


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## egenest (Jan 25, 2004)

I have the 2007 GMC Duramax and am getting 20.3 when I drive any long distance with a mixture of terrain and speed limits. But I am trying to get that by not accelerating to fast and staying at the posted speed limit or a little less.
I have not towed a trailer with it yet, that will come this weekend when the new Sydney 31FRKS arrives. At this point I have 3,100 miles on the truck. It is fun to try to get the MPG up there, but I can't do it with a lead foot.
Ed


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## PDX_Doug (Nov 16, 2004)

No personal diesel experience here, but what I hear from the oil-burner types around here (at work), is that 20,000 miles is kind of the magic number.

Happy Trails,
Doug


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## dougdogs (Jul 31, 2004)

Steve, How fast were you going when towing??

The duramax turbo really gets thirsty when you are going over 65mph


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## NJMikeC (Mar 29, 2006)

Don't necessarily pay so much attention to other peoples numbers because they are filled with variables and some times they read off the computer and get an instantaneous number and tell you that one.

The variables are: wind, A/C, speed and the number of hills. The hills will get you for sure because you don't back off with the diesel but it is drinking fuel dragging in my case 16K pounds up the hill at 63MPH.

I guess they break in when they break in would actually be the best answer I can give you. I'm at 11.5MPG pulling a 9K lb 5'er, A/C on and mostly up and down hills. I get 12+ not in the hills from what I can tell. Almost 15K miles and haven't noticed an increase in mileage other then it really stinks using winter fuel in 10 degree temps.

Another thing don't compare yourself to a 5.9L Cummins and in some cases the Powerstroke. You have more power then them and the LBZ DMAX shows it in MPG. I myself wish I had the LLY motor but what do ya do! We will see the reports on the 6.4L Ford and 6.7L Cummins soon enough and they will likely take the hit from the increased power #'s.


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## Y-Guy (Jan 30, 2004)

When I had our F350 everyone kept telling me it got better about 20,000 miles. I got a pretty consistent 12 MPG towing our loaded Raptor which I was more then happy with. Around town though I wasn't do better then 14 when I was empty. I had well beyond 20k and hadn't seen any huge gains. I was fine with 12 it was the town miles that were killing my pocket book. The more miles you put on the better mileage you should see. As said before chill on the quick starts if you can and take it easy on the acceleration.


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## tdvffjohn (Mar 10, 2005)

Another thing to be careful when comparing...1/2 ton, 3/4 ton, gear ratios and the all important driving habits. Wind and hills on long trips make a difference. I waxed my minvan once before I drove home from Arizona and my mpg was worse, go figure. I also don t care what mythbusters said, a covered pick up bed makes a difference.


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## GoVols (Oct 7, 2005)

You oil-burners stop your whining. I get around 7-9 MPG towing my little 26RS.


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## Rollrs45 (May 7, 2007)

I have a 2004 Duramax with 55K on the odometer. I get around 11 mpg when towing, but mind you that's running 65 mph. You could always buy a tuner and download the software. For intstance, I'm looking at the Diablo Sport Diesel tuner. Everyone says I'll increase my mpg while the company claims an increase of 65 hp and 134 ft. lb's of torque . I'll eventually add a 4 inch cat back exhaust and maybe a cold air induction kit, which should get me even better performance and mileage.

Mike


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## Bill H (Nov 25, 2006)

Here's what I just saw today. I had to take about a 35 mile trip down the Highway so I reset the eco avg reading. By the time I got off the highway, I had topped at 22 MPG A/C on. Then I had to to some slow driving and a couple of stops on the site. I got back on the highway and was at 20.1 most of the return was up hill and by the time I got back off the highway, I was looking at 20.2 . Now I can't complain about that. When I was towing this past weekend, I saw about 11 and that was through a lot of hills. I get a better estimate when I go to Virginia this summer.


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## rms0726ea (Aug 9, 2006)

I don't know how accurate the MPG "lie-O-meter" is on the console on the Dmax, but the one on my F-250 can be off a few mpg compared to manual computation.


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## Steve McNeil (Aug 30, 2004)

dougdogs said:


> Steve, How fast were you going when towing??
> 
> The duramax turbo really gets thirsty when you are going over 65mph


I was towing at 68-69mph.


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## rms0726ea (Aug 9, 2006)

Steve McNeil said:


> Steve, How fast were you going when towing??
> 
> The duramax turbo really gets thirsty when you are going over 65mph


I was towing at 68-69mph.
[/quote]

Steve,

What size trailers where the two of you towing? TT or 5th Wheels?

Rich


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## Steve McNeil (Aug 30, 2004)

White Buffalo said:


> Steve, How fast were you going when towing??
> 
> The duramax turbo really gets thirsty when you are going over 65mph


I was towing at 68-69mph.
[/quote]

Steve,

What size trailers where the two of you towing? TT or 5th Wheels?

Rich
[/quote]

Rich,

Both of us have tt's. His is the 25RSS and mine is the 28 RSS. Don't get me wrong, the mileage is much better than the gas model. I keep hearing and seeing much higher mpg, and would love to acheive it.

Steve


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## rms0726ea (Aug 9, 2006)

That explains some of the difference, yor trailer is a bit bigger & probably heavier.

One more question Steve,

where you computing the MPG by hand or reading the overhead console?

Rich


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## Steve McNeil (Aug 30, 2004)

White Buffalo said:


> That explains some of the difference, yor trailer is a bit bigger & probably heavier.
> 
> One more question Steve,
> 
> ...


We was both looking at the computer reading.

This may be a dumb question, but how do you tell if you have the LBZ or the LLY? And what is the differance?
Everything that I can find only shows it as a 6.6 Turbo diesel.

Steve


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## map guy (Jan 11, 2007)

Steve McNeil said:


> That explains some of the difference, yor trailer is a bit bigger & probably heavier.
> 
> One more question Steve,
> 
> ...


We was both looking at the computer reading.

This may be a dumb question, but how do you tell if you have the LBZ or the LLY? And what is the differance?
Everything that I can find only shows it as a 6.6 Turbo diesel.

Steve
[/quote]

Steve.
Engine is identified by the vin number. Look at the 8th digit per this copy and paste from kennedydiesel.com

Engine Identification: 
The Duramax engine has evolved from the original LB7 series to the LLY series, and now the LBZ series. The LB7 was used from 2001 model year until mid 2004 model year. In mid 2004 the LLY was released. In 2006 the Duramax changed again. The early 2006 engines were still called LLY and the alter 2006 became the LBZ. This creates some confusion as the 06 LLY is distinctively different from the 04.5-05 LLY. The 2006 LLY and LBZ engines are essentially the same when it comes to modifications. The simplest way to verify which series you have is the VIN# of the truck. The 8th digit is the engine ID and it will either be a 1, 2, 3, or D.

01-04 LB7 is a 1 
04.5-05 LLY is a 2 
06 LLY is a 3 
06 LBZ is a D

Map Guy


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## Bill H (Nov 25, 2006)

map guy said:


> That explains some of the difference, yor trailer is a bit bigger & probably heavier.
> 
> One more question Steve,
> 
> ...


We was both looking at the computer reading.

This may be a dumb question, but how do you tell if you have the LBZ or the LLY? And what is the differance?
Everything that I can find only shows it as a 6.6 Turbo diesel.

Steve
[/quote]

Steve.
Engine is identified by the vin number. Look at the 8th digit per this copy and paste from kennedydiesel.com

Engine Identification: 
The Duramax engine has evolved from the original LB7 series to the LLY series, and now the LBZ series. The LB7 was used from 2001 model year until mid 2004 model year. In mid 2004 the LLY was released. In 2006 the Duramax changed again. The early 2006 engines were still called LLY and the alter 2006 became the LBZ. This creates some confusion as the 06 LLY is distinctively different from the 04.5-05 LLY. The 2006 LLY and LBZ engines are essentially the same when it comes to modifications. The simplest way to verify which series you have is the VIN# of the truck. The 8th digit is the engine ID and it will either be a 1, 2, 3, or D.

01-04 LB7 is a 1 
04.5-05 LLY is a 2 
06 LLY is a 3 
06 LBZ is a D

Map Guy
[/quote]

SO what were the main differences between these versions and which were better? I remeber hearing that some of the LLY's had an over heating problem.


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## beachbum (Nov 27, 2006)

Steve McNeil said:


> I am wondering when the fuel mileage increases on the duramax. I bought a 2006 GMC 2500 back in August. I have approximently 7700 miles on it. I towed my 28 RSS approx. 900 miles round trip this past weekend, mainly flat lands with a few big inclines. I am getting 14 mpg in town/highway (mixed-normal daily driving). I was only getting 10.6 mpg while towing this weekend. I had people tell me that their diesel trucks are getting 20 mpg on the highway and 14 mpg while towing. My friend just bought a used 2006 Dodge 2500 Diesel with appprox. 16,000 miles on it and was getting 14 mpg on our trip. What is the secret in better mpg on these diesels?
> 
> Thanks Steve


Bought new '06 in August of last year and you put 7700 miles on it. Man!! I bought an 07'classic in December of 06 and already have 14500 miles. Mileage around the county is 16-18 miles. towing is still only around 10-12. Just had oil analysis done by Blackstone and they said still not broken in. (2nd oil change) Had 10% oil life left on computer, 8909 actual miles on oil. their analysis was that oil still had plenty usable life. Seems I never take short trips. Everything is 30 minutes away from where we live, so it's easy to rack up the miles.
david


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## Swany (Mar 2, 2006)

Steve McNeil said:


> I am wondering when the fuel mileage increases on the duramax. I bought a 2006 GMC 2500 back in August. I have approximently 7700 miles on it. I towed my 28 RSS approx. 900 miles round trip this past weekend, mainly flat lands with a few big inclines. I am getting 14 mpg in town/highway (mixed-normal daily driving). I was only getting 10.6 mpg while towing this weekend. I had people tell me that their diesel trucks are getting 20 mpg on the highway and 14 mpg while towing. My friend just bought a used 2006 Dodge 2500 Diesel with appprox. 16,000 miles on it and was getting 14 mpg on our trip. What is the secret in better mpg on these diesels?
> 
> Thanks Steve


Using a Dodge w\ 5.9 Cummins. It has about 8000 miles on it. I tow a 27 RSDS. My around town MPG no trailer is a solid 17.5. Highway empty @ 60 MPH is 22. Highway empty at 70 MPH is 21. Towing, last trip to Northern CA from Puget Sound area over the Siskious (spelling?) 12.4. Used to manage a fleet of on highway freight trucks and it took at least 60K miles and up to 100K to loosen those guys up. Don't know yet about this one.


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## NJMikeC (Mar 29, 2006)

On the differences between the '06 LLY and the '06 LBZ, programming only.

On the difference between the '06 LLY and the 04-05 LLY. Variable Vane Turbo, a lot of programming differences, cooling system, intake system, reduced compression. Also if you have an '04 to '05 LLY you probably have the 5-speed Allison.


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## Steve McNeil (Aug 30, 2004)

beachbum said:


> On the differences between the '06 LLY and the '06 LBZ, programming only.
> 
> On the difference between the '06 LLY and the 04-05 LLY. Variable Vane Turbo, a lot of programming differences, cooling system, intake system, reduced compression. Also if you have an '04 to '05 LLY you probably have the 5-speed Allison.


Looks like I have the '06' LBZ

Steve


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## Bill H (Nov 25, 2006)

NJMikeC said:


> On the differences between the '06 LLY and the '06 LBZ, programming only.
> 
> On the difference between the '06 LLY and the 04-05 LLY. Variable Vane Turbo, a lot of programming differences, cooling system, intake system, reduced compression. Also if you have an '04 to '05 LLY you probably have the 5-speed Allison.


I have the 04 LB7.....


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## hatcityhosehauler (Feb 13, 2004)

I think in general, your going to see in town mpg's of between 12-14 depending on your particular driving style, and maybe the same or a little less while towing. Highway only, and you'll see the 20+ mpg's, again dependent on your particular driving style.

Driving style has more to do with it then many think. Any of the current light duty diesels that are used in pickups are fuel hungry above 2000 rpm. It's the nature of the beast.

My Excursion, and an '04 6.0L PSD and 3.73 rear end gets 20 mpg highway, not towing, at 68 mph (right around 2000 rpm). I go any faster and that starts to drop quick. On a trip to Hilton Head over the winter, I averaged 18.5 through South Carolina, with the cruise set at 75.

At every fuel stop, I fill up, and use both the "lie-o-meter" and I also hand calculate each tank. My wife says I'm obsessive/compulsive. I keep a running spreadsheet with the totals since I bought the truck and can tell you my cost per mile in any given tank full, or quarter.

The on board computers are not as inaccurate as people think. The computer knows how much fuel is delivered to each injector, and how many miles have been traveled. I think most of the discrepancies between hand calculation and the computer are operator error, unless you can be sure that the fuel is being filled to the same exact spot every time. I find that difficult to confirm. Also, I reset my computer at every fill up, so the average that is showed if for the current tank full only, and I have noticed more consistancy between the hand calc method and the computer since I've been doing that.

Good luck with your Dmax

Tim


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## Brew (Apr 27, 2007)

Unfortunately with the Duramax fuel mileage is not the best. I have owned a 2003 Dodge Ram with the Cummings and now a 2004 Chevy with the Duramax. I think I should of kept the Dodge it was far better in fuel mileage. Now with the Duramax on the Hwy if you keep it at 60 mph that will give you the best anything over and you will see it drop fast. I just did a trip from Vancouver B.C to Des Moines Iowa and drove down empty at an average 70 to 75 mph and got 17.49 us mpg or 21.00 imperial mpg. This was hand calculated cause most time the on board computer is off. On the way back towing a Thoroughbred T-271 4800 Lb. travel trailer I got 9.92 us mpg or 11.91 imperial mpg. With the Cummings I would get 22 us mpg and with a heavy foot it would drop to 20.5 to 21 mpg empty and I towed a Jayco 29Y 6500 Lb. loaded and would get 13 to 14 us mpg with a heavy foot. Putting a chip or program booster on a Duramax will give you more power but really has not fix the fuel mileage problem. I have been reading lots of forums to see if anyone really has the fuel mileage issue with the Duramax solved yet but I have not found any as of yet that has be proven without a doubt. You can go to

http://www.thedieselgarage.com/forums/index.php?

And find lots out there or if you own a Dodge a really good site is

http://www.dieselram.com/index.html


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## ARzark (Aug 9, 2005)

hatcityhosehauler said:


> Driving style has more to do with it then many think. Any of the current light duty diesels that are used in pickups are fuel hungry above 2000 rpm. It's the nature of the beast.
> 
> Tim


Ain't that the truth! I do notice a drop in mpg over 2000 RPM.


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## dougdogs (Jul 31, 2004)

NJMikeC said:


> On the differences between the '06 LLY and the '06 LBZ, programming only.
> 
> On the difference between the '06 LLY and the 04-05 LLY. Variable Vane Turbo, a lot of programming differences, cooling system, intake system, reduced compression. Also if you have an '04 to '05 LLY you probably have the 5-speed Allison.


Plus 05 LLY to 06 LLY had a difference in the engine rev limiter and tachometer. My 05 was limited to around 3K, on 06's the tachometer displays to 5 or 6K (not sure what the limit is though)

Best milage I got with my 05 was 24.3 not towing, and not going over 65mph. Don't trust the dashboard gage, use your own calculator. Worst mileage I got towing was 11.4 but it was a up and down Pocono mountain in PA 4 TIMES!! (don't ask, my wife was "Nagivator" on that trip!) ((towing 28FRLS 5th wheel))


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## jdpm (Apr 12, 2007)

I have a '06 Dodge RAM 2500 Quad Cab 4x4 with short box and 3.73 rear axle. I tow a 31FRKS fiver with an empty weight of 8100lbs. The truck just turned 15k and I get about 9mpg at 70-72 mph with the air and cruise. Thats here in FL where it's pretty flat. Anything over 2000 rpm kills the mileage whether solo or towing. Driving the same way solo, I still have never gotten over 16.8mpg. People stay say give it 20-25k miles till break in. I'd e VERY happy if in the end it got 12-13 towing at 70mph, but I'm not getting myhopes up. I still prefer a diesel or a gasser for towing any day. PCM


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## Swany (Mar 2, 2006)

jdpm said:


> I have a '06 Dodge RAM 2500 Quad Cab 4x4 with short box and 3.73 rear axle. I tow a 31FRKS fiver with an empty weight of 8100lbs. The truck just turned 15k and I get about 9mpg at 70-72 mph with the air and cruise. Thats here in FL where it's pretty flat. Anything over 2000 rpm kills the mileage whether solo or towing. Driving the same way solo, I still have never gotten over 16.8mpg. People stay say give it 20-25k miles till break in. I'd e VERY happy if in the end it got 12-13 towing at 70mph, but I'm not getting myhopes up. I still prefer a diesel or a gasser for towing any day. PCM


The point at which the MPG stars dropping off is over 1800 RPM


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## nynethead (Sep 23, 2005)

I have the 06 chevy 2500Hd lbz duramax. Around town with stop and go traffic as my daily driver I get 16mpg. If I watch my acceleration and behave I can get 18 around town. pushing 70-72 on the highway with no tow I get 19.

I currently just turned 14,000 miles. towing a trailer, when it was brand new and I towed my 29BHS at 70-72 MPH i was getting 14MPG down tha GSP to the jersey Shore. I now have a 9K Laredo 30BH which is 35 foot and without trying to save fuel, such as fisrt out of the gate at the tolls and passing to get through traffic traveling at the same 72 MPH I have been averaging 11 MPG.

I keep saying I am going to slow down to 60-65 and see how much difference it makes in MPG, but I am always looking to get where I am going to enjoy my time off.

I usually drive with the AC on and use cruise control to maintain speed. Hills or not, AC or not diesel maintains speed pulling the 5'er and always has more in reserve.


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## rms0726ea (Aug 9, 2006)

nynethead said:


> I keep saying I am going to slow down to 60-65 and see how much difference it makes in MPG, but I am always looking to get where I am going to enjoy my time off.
> 
> I usually drive with the AC on and use cruise control to maintain speed. Hills or not, AC or not diesel maintains speed pulling the 5'er and always has more in reserve.


I second that!
I'm the same way.


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## Rollrs45 (May 7, 2007)

Even on the worst day it beats what I was getting with my gasoline powered Yukon. Not to mention I have the power and no longer worry about hills or inclines. 








Mike


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## CautiousCamper (Jun 27, 2006)

My experience with diesel cars and trucks owned is that the mpg does not necessarily increase because the cylinder compression ratios are so high for diesels in the first place. As they wear, I would expect mileage to go down over time. 
Gas engines always were thought to get better mileage after a 
"breaking in" period. That may be old school, but it makes a lot of sense. I wouldn't expect diesel mileage to go up much at all from new.


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## skippershe (May 22, 2006)

CautiousCamper said:


> My experience with diesel cars and trucks owned is that the mpg does not necessarily increase because the cylinder compression ratios are so high for diesels in the first place. As they wear, I would expect mileage to go down over time.
> Gas engines always were thought to get better mileage after a
> "breaking in" period. That may be old school, but it makes a lot of sense. I wouldn't expect diesel mileage to go up much at all from new.


Great...the dually now has about 1,000 miles on it, so we're only going to get 13.7 mpg from now on?


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## GarethsDad (Apr 4, 2007)

Ok heres one for you. My van at work just had a new engine installed (long block) due to dealer screw up. The new engine is slowly gaining more power going up hills, with the old engine i could hit a hill at 65 and pick up speed to the top of the hill. Now with the new engine i hit the hill at 65 and i'd be lucky to be going 55 by the time i hit the top. With 1500 miles on the new engine it will hold 65 up the hill. With the high compression ratio along with all of the stiff new parts causing friction the engine is fighting itself untill it loosens up and drops the friction. The van is a 6 ton chevy 12 ft cube with a 6.5ltd and a 4 speed trans with OD and 4:80 gears. James


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## Collinsfam_WY (Nov 9, 2006)

skippershe said:


> My experience with diesel cars and trucks owned is that the mpg does not necessarily increase because the cylinder compression ratios are so high for diesels in the first place. As they wear, I would expect mileage to go down over time.
> Gas engines always were thought to get better mileage after a
> "breaking in" period. That may be old school, but it makes a lot of sense. I wouldn't expect diesel mileage to go up much at all from new.


Great...the dually now has about 1,000 miles on it, so we're only going to get 13.7 mpg from now on?








[/quote]

Skippershe - my buddy at work has a 1 ton dually QuadCab 5.9 Cummins. He gets "about 20" on the highway. I asked him about mileage pulling and he said "I don't know but she runs good pulling my loaded horse trailer at 80". From all I have read (no personal experience), your Cummins will improve on fuel mileage until it is broken in. I have read posts from many diesel owners send their oil off to get it tested to see if their motors are broken in or not. I have no personal experience outside of reading posts from those who have Cummins diesels and most of them are reporting 30k-40k miles to break in and their fuel mileage increases from new until around then. Some say they get 22 unloaded on the highway but I doubt a dually like yours will ever reach that.









Good luck!

Curtis


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## skippershe (May 22, 2006)

collinsfam_tx said:


> Skippershe - my buddy at work has a 1 ton dually QuadCab 5.9 Cummins. He gets "about 20" on the highway. I asked him about mileage pulling and he said "I don't know but she runs pulling my loaded horse trailer at 80". From all I have read (no personal experience), your Cummins will improve on fuel mileage until it is broken in. I have read posts from many diesel owners send their oil off to get it tested to see if their motors are broken in or not. I have no personal experience outside of reading posts from those who have Cummins diesels and most of them are reporting 30k-40k miles to break in and their fuel mileage increases from new until around then. Some say they get 22 unloaded on the highway but I doubt a dually like yours will ever reach that.
> 
> 
> 
> ...


Thanks for the confidence booster Curtis








We are at least hoping for 17-18 highway, guess only time will tell...


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## Oregon_Camper (Sep 13, 2004)

skippershe said:


> Thanks for the confidence booster Curtis
> 
> 
> 
> ...


18mpg would be a DREAM!!!! I go downhill and it moves to 10mpg and I'm thrilled.


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## Collinsfam_WY (Nov 9, 2006)

I wish I knew what I got - my gen-u-wine Ford odometer doesn't work most of the time nowadays so I can't tell what I mpg I get when towing. I would guess that I get around 8. Maybe. In a headwind? Forget it - try something like 5 lol.

-CC


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## johnp (Mar 15, 2004)

With 1100 miles on mine I have been getting 18-20 on the highway if I keep it under 70 and 15 around town.

John


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## Lazybonz(aka Bill) (Sep 23, 2006)

I case anyone is interested

Just thought I would update folks on mileage etc..
I have a 2007 Chevy 2500 HD Silverado Classic 4X4 w/ Duramax/6 speed Allison. It is the extended cab work truck package. I bought it brand new in Nov. It now has 7500 miles on it. I tow a Outback 26RKS. 
When towing I average 10-12 mpg. 
Without towing, I can get anywhere between 15-21 depending on when and where and how I drive it. I must say that I don't see above 17-18 often, but I have gotten that a few times on long flat runs below 65 mph.
Towing in heavy wind I have gotten below 10 mpg, and have gotten a bit better than 12mpg. on a long slow trip.
I am thrilled with the truck. My mileage is better but not the whole story...

My old Dodge Ram 2000 with a 5.9L V8 used to get 5-6 mpg towing and maybe 12 without the trailer no matter what I did. I ued to be white knuckled on every trip while the truck struggled up and down hills at 3500rpms shifting like crazy with the trailer.















The Duramax runs all day at below 1800 rpm up any hill or mountain without a whimper. I relax and can actually enjoy the ride. I barely know the trailer is behind me.
Pure pleasure...worth every nickel.









Bill


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## rms0726ea (Aug 9, 2006)

> Thanks for the confidence booster Curtis
> 
> 
> 
> ...


It will go up over time as the engine breaks in. I bought mine with 24K on it and I have seen the highway mpg go up about 2 mpg after 50K.


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## OutbackPM (Sep 14, 2005)

I have about 18000 on my truck and have not noticed any increase in mpg. There are too many other variables that effect it to weed out say a 1-2 mpg improvement. Wind is a very big factor when towing and warm up time is very long on a diesel compared to a gas. With temp in the upper 80's my mpg is about 16-17 in a week campared to 14-15 in winter. If I drive a good distance after warm up I don't see any difference from winter to summer. This year I put in synthetic oil with the hope that this will give me a little improvement in the colder months (as well as better lube in general).

I have read where diesel take 15-20K to break in but I would believe that has to depend on its use. If you run empty all that time I am sure it won't compare to one that has towed even a small portion of that mileage.

Another factor that influences mpg with time is the wear state of the tires. More wear gives lower rolling resistance so may give the impression its the engine break in. When you put new tires on it would come down to where you started. I saw this on 2 sites one I know was the Cummins site which was aimed more at 18 wheelers than pick ups.


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## dougdogs (Jul 31, 2004)

OutbackPM said:


> With temp in the upper 80's my mpg is about 16-17 in a week campared to 14-15 in winter.


Diesel fuel is bended differently (additives) in the winter, than it is in the summer. A little less mileage in winter is completely normal.

When towing, air pressure in the trailer tires can have a big effect on MPG. My new trailer is over 7000 pounds heavier, and 5 feet longer than my 28 FRLS was, but I get over 1 MPG better milage when towing my new trailer, than I did with my outback.

My new trailer tires need 110 PSI and I used to tow my outback at 55-60 PSI. Big difference in static rolling resistance. I don't remember what the max PSI was on the tires of my outback, but I wish I had been running them at max pressure.

Doug


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## sleecjr (Mar 24, 2006)

jdpm said:


> I have a '06 Dodge RAM 2500 Quad Cab 4x4 with short box and 3.73 rear axle. I tow a 31FRKS fiver with an empty weight of 8100lbs. The truck just turned 15k and I get about 9mpg at 70-72 mph with the air and cruise. Thats here in FL where it's pretty flat. Anything over 2000 rpm kills the mileage whether solo or towing. Driving the same way solo, I still have never gotten over 16.8mpg. People stay say give it 20-25k miles till break in. I'd e VERY happy if in the end it got 12-13 towing at 70mph, but I'm not getting myhopes up. I still prefer a diesel or a gasser for towing any day. PCM


I get about 11.5 towing at 68. Welcome BTW glad to have another north florida outbacker!


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## NJMikeC (Mar 29, 2006)

I might have just witnessed my truck break in @ 15K miles. I'm now in the mid to high 16MPG around town where I was mid 15 before. I'll likely never know what highway unloaded mileage is because I'm always towing.


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## hatcityhosehauler (Feb 13, 2004)

dougdogs said:


> My new trailer tires need 110 PSI and I used to tow my outback at 55-60 PSI. Big difference in static rolling resistance. I don't remember what the max PSI was on the tires of my outback, but I wish I had been running them at max pressure.
> 
> Doug


Wow..What do you have on the new 5'er? Tractor trailer tires? The tires on our fire trucks are filled to 120psi.

Tim


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## jdpm (Apr 12, 2007)

My 06 RAM diesel was getting 8-11 mpg solo when new and all it has done is slowly get better. It know has 18k miles on it and is getting 10mpg towing and 13-17 solo. The cumins is a strong, tight engine with a great reputation for reliability and long life. Depending on how it's used, it can take up to 50k miles to be broken in. The best way to do it is working it with a load and the number of engine warm up coll down cycles - that is directly form the Cummins web site. For you guys with the CUMMINS that are interested in more info, tips and performance questions, chcek out http://www.dieseltruckresource.com/ pcm



Rollrs45 said:


> Even on the worst day it beats what I was getting with my gasoline powered Yukon. Not to mention I have the power and no longer worry about hills or inclines.
> 
> 
> 
> ...


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## tx_roundman (Jan 27, 2007)

Just got in from Sturgis SD. Traveled 1370 miles X 2 using a total of 251 gallons. Most times trying to keep speed around 70 MPH. Pulling a friends Victory Lane Toy Hauler weighing apx. 16,000 with 2 bikes. I was very please with the fuel mileage being 10.9 the indicter on the roof console showed 12.1

My friend was very reluctant to take his new Ford 6.7 getting 8-9 miles a gallon with the same trailer. Both trucks are Diesel


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## GoVols (Oct 7, 2005)

Brand new 2007 Silverado Classic 2500HD with LBZ Dmax/Allison. First tank, mixed driving, 16.9 MPG and keeping the speed under 60 mph; second tank 18.0 MPG predominantly highway speeds of 55-70 mph. Mileage hand calculated !
















Current tank is B20 biodiesel, so we'll see how that does.


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## jdpm (Apr 12, 2007)

jdpm said:


> Even on the worst day it beats what I was getting with my gasoline powered Yukon. Not to mention I have the power and no longer worry about hills or inclines.
> 
> 
> 
> ...


[/quote]
UPDATE on my MPG! My truck has just turned 20k miles and about 6k of that has been towing. It has been in the shop a few times for poor performance and smoking upon start up. FINALLY, they figured it out. It needed to have ALL 6 injectors replaced and a reflash of the on board computer. It now is quieter and runs SO much better. The solo mpg is now 19.2 mpg here in FL on the interstate with the cruise set at 70mph and the ac on. Have not towed with it yet since out of the shop. Looking forward to it. Should now get closer to 13 as I have been wishing for. For towing, no gasser for me!


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## sleecjr (Mar 24, 2006)

jdpm said:


> Even on the worst day it beats what I was getting with my gasoline powered Yukon. Not to mention I have the power and no longer worry about hills or inclines.
> 
> 
> 
> ...


[/quote]
UPDATE on my MPG! My truck has just turned 20k miles and about 6k of that has been towing. It has been in the shop a few times for poor performance and smoking upon start up. FINALLY, they figured it out. It needed to have ALL 6 injectors replaced and a reflash of the on board computer. It now is quieter and runs SO much better. The solo mpg is now 19.2 mpg here in FL on the interstate with the cruise set at 70mph and the ac on. Have not towed with it yet since out of the shop. Looking forward to it. Should now get closer to 13 as I have been wishing for. For towing, no gasser for me!
[/quote]

glad to here you got it fixed!


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