# Duramax 12.5 miles per gallon



## mullet man (Jul 8, 2009)

i have a 08 duramax 2wd with 15000 miles. no mods done, computer says 13.5 mpg on mixed driving, 12.5 when checked manually. everyone else tells me 16-18mpg even on 4wd. What could be the problem? i asked dealership and they say it's normal or that they don't know.


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## Profish00 (May 21, 2004)

Big truck owners lie...It's a diesel/green thing


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## Arlon (Feb 8, 2005)

I get 12.5mpg too (hand calculated ). But I have a cummins and that's while towing a 10,000lb GVW 5th wheel trailer (2003, 3/4 ton, 2wd, 3.73 gears). (-:}

Mileage on all of the "smog dog" diesels is pretty miserable from all I've heard. Govt. doesn't want you driving a diesel for some reason and they are doing everything they can to take away the diesel advantage. I'll keep owning diesels but I doubt I'll ever own a newer one. I'll keep rebuilding older ones.


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## DSL_PWR (Jul 22, 2009)

With the 08 you have all the emissions **** on the truck which greatly lowers the mpg of the truck. I had an 04 LB7 and 06 LBZ GMC duramax's and was getting well over 17 in town and 24 on the highway with both trucks but most of what I have read on the newer trucks you are in the ball park of mileage. 

Can always add a programmer and remove the DPF emission stuff. 

I have an 08 Ford F-250 now and I get 14-16 in town and 19+ on the highway with proper tuning and exhaust mods.


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## bigfishtx (Jul 17, 2007)

We left out to west Texas about five years ago, with a Dodge 5.9, and Ford Powerstroke 6.0 and a Chevy with Duramax. All three trucks were towing jeeps on Trailers, and had similar loads.

They all three got about the same mileage, around 10. The Cummins got about a half MPG better on average. The Ford had the most power on long hard climbs.

In Honesty there is little difference in all the big three's diesels. 

When you hear these wild claims of great mileage, listen to what they are saying. It is usually something like "I CAN get 18 MPG on the Hwy". That is a lot different from I DO get 18 MPG.

I have a Dodge 1 ton with 5.9 and I CAN get 18-19. I usually get around 14-15 empty.


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## Empty Pockets CC (Feb 18, 2009)

Rip all of the emissions garbage off. They make programmers to fool the ECU. You will get your money back that you spent on these mods in about 6 months depending on how much you drive. If you're concerned about warranty find a cool dealer or don't do it. I have a '07 dodge with the 6.7 cummins. Voided every kind of warranty 50 miles off of the lot and haven't looked back. The dealer was calling me to ask where I got the stuff to rip that california queer garbage off. They're sick of desooting motors and replacing turbos too. Their customers are sick of being without their trucks. I'm sick of the ignorant govt. sticking their nose in my business. Stick it to the man...

Also, find a good air intake. The stock ones are restrictive and trash. "Can" and "Get" are very big factors too. bigfishtx made a good point. 

Intake, no dpf/cat, programmer, and rip/delete the EGR valve. If you're going to keep your truck for over 150,000 miles these mods are a must. The heat and soot will kill you motor prematurely if not...


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## General CoolBro (Jun 13, 2005)

Get 16.7 avg city/hwy. Best highway at 70 MPH calculated 19.8 mpg. Usually average around high 18's on highway - no trailer. 
4x4 CC with 32.5" tires - Duramax LLY.

Two things;

EGR blocker plate
Large exhaust with cat removed.

GCB


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## camowag (Aug 25, 2005)

15k miles not even broke in yet


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## LDBuckslayer (Sep 12, 2005)

I have an 08 4x4 crew cab with the D MAX. I drive 50 miles round trip to work all stop and go and I average 15 to 16 . Mine goes into regen once per tank. On the highway I have seen 19, that was empty and driving 70.


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## TheDingy (May 13, 2009)

With 15k miles it is going to get better until about 30k also slow down :-D that will help greatly. 

I have had many different of the 07-09 duramax's and we get about 11.5 towing with them and 15-18 running them down the road at 65 or 60. The speed is a huge difference in the mpg.


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## quickrick (Aug 10, 2009)

*DuraMax mpg*

I have to agree with CAMOWAG. 15K miles is not even close to being "broke-in". Mileage will definitely increase as friction reduces in engine.


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## livetofish (May 22, 2004)

I am at 110K miles on my 2003.

18-20 mpg on my runs to Palacios or Rockport without trailer. 10-12 mpg with travel trailer. The truck does not see city streets very much so can't comment there.

I hold around 2K rpm which puts me between 62-65 mph. At higher rpm, I found, that the mpg drops off quickly.


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## Cudkilla (Nov 5, 2004)

I have a 07.5 LMM and get about 15-16mpg 50/50 city/hwy. 50K miles on clock. Austin to Houston not towing at 70 mph I can get about 18-19 mpg but about 22 mpg coming back. Go figure..maybe the headwind or grade?  I get about 12 mpg with a 4000 lb Mako 2201 with a t-top and in tow/haul mode Austin-Rockport.

It really depends on how heavy your foot is. If I drive a bit hard, mpg goes down quite visibly. If you're pushing past 2100 rpm every time you get going, you're gonna see your mpg go down. I also had my ECU reflashed during a recall and it seems to regen less often than once per tank. Maybe now once every 2-3 tanks. I get 12.5 mpg on the DIC during regens.

I use a PPE programmer now on level 3 with stock equipment and get a bit less mpg but mainly because I'm having way too much fun now! NEtx step is seriously considering the EGR and DPF delete mod. Mainly I am concerned about the inspections if I do the exhaust mod.


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## BIG PAPPA (Apr 1, 2008)

*FYI GUYS*

Be careful hammering down on these GM Diesels with programmers if the truck is still under warranty. The PCM records the highest Turbo boost and if you boost over 650, you are Tattoo'd for warranty if they want a Snapshot from your PCM. Smoke a Turbo and you will see what i'm talking about. I used to tell people to go ahead and install their programmers, but now i have to tell them to wait until the 100k warranty is over.
as far as Mileage, my 2004 LLY Duramax gets a real 17 mpg average and 19-20 highway. Mods: 5" exhaust downpipe back, no Cat and Hyper Tech programmer on Tow safe mode. PS, my mileage was at 14.5 until 35,000 miles and it jumped up again at 80,000 miles. i have 147,000 on it now and have held back getting a new one due to all the epa/federal **** on them. Next generation of diesels will be like a chemical plant rolling down the road. you will have to by a cleaner that your truck will use during regeneration of the exhaust filters.


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## gitchesum (Nov 18, 2006)

Rule #1.

If you modify a vehicle from stock, you should expect to pay any driveline repairs from that point on.


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## noskunks (Jul 27, 2006)

Profish00 said:


> Big truck owners lie...It's a diesel/green thing


yeah that too!!

I drove an '05 2500 HD w/duramax and got 13-16. When I started running the ULSD it dropped down to about 12-12.5. Pulling a 28' 9k TT I got about 9.

also drove an '08 F350 w/ 6.6 powerstroke, with very similar results. It got only slightly better economy on the ULSD than the duramax I think the duramax had more power but the ford felt way more solid.


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## ferd (Mar 12, 2009)

*why I have not gotten..*

I have not gotten rid of my 96 F350 Diesel with the hwy rear end. ...I do get 20 mpg to the gal hwy and 16-18 around town. and I am rolling over the big 300,000 miles probably next week. I got 14 pulling a gooseneck with steers and equiptment to the big livestock shows in Texas. still gowing strong just the darn ol I beam front ends .. Ihave those worked on a few times...BUT IT IS PAID FOR!


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## sboudreaux (May 22, 2008)

Mullet Man - That sounds out of wack to me. I know a few guys running 4X4 duramax's & they are doing better than 12.5 with the hammer down. I would check with another dealer before I accepted it as okay mileage. My 2 cents....


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## 4Rodsfishing (Oct 27, 2009)

I have a n 06 Dmax 4x4 crew cab. It does not seem to matter what I am towing, my AquaSprot 215 about 4000lbs or my tailer with ATV's my truck averages 13.5, empty I am averaging 15-16 city/highway. I only wish I had a bigger fuel tank


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## Arlon (Feb 8, 2005)

4Rodsfishing said:


> I only wish I had a bigger fuel tank


Bigger tank is way cool. I got a 45gal ATTA tank installed a few weeks ago and we tested it on a drive to Arkansas last week.

Filled both tanks in Houston. Towed 5th wheel from Houston to Caddo lake, explored there for a few days, towed to Petit Jean SP in Arkansas, explored a few more days.. Finally filled up in Russelville (54 gallons). Explored west Arkansas for a few more days, towed back to Caddo explored a few more days then towed back to Houston. Got back with half of my main tank still full, took another 54.5 gallons to fill both tanks.

Getting to drive 1522 miles with one fill up (totally at my convenience) was pretty cool. That added tank gives me about a 900 mile towing range with the 5th wheel and about 1500 miles on the freeway without it.. (-:}

That tank when full and bed empty really helps the ride too.. Only regret I have is not having done it 5 years ago when I got the truck!


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## mas360 (Nov 21, 2006)

I have a Ford F250, year 2000, 2WD with 120K miles on it. This is bone stock with only an upgrade intake. I make 16.5 mpg in city driving, short distances of less than 5 miles. My driving habit is to keep rpm under 2K all the times. 

I've been told Duramax renders much better mpg than Powerstroke.


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## thebach (Apr 13, 2005)

2006 F250 4x4 diesel; drive from Houston to Junction and average 19mpg driving between 75-85. I do have a bed cover and 96,000 miles. I swear in the last 12,000 miles this truck is getting better and better mpg's.


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