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Having owned a '01 which was getting 23 mpg on the highway and 19 mpg in town, I am very frustrated with my '05. God help me if I hitch-up my 25 foot flatbed. My mileage drops to 10 mpg!! With my '01, I was getting between 15 and 16 mpg -- loaded. Chevy has taken what was an excellent engine and tranny combination and created a fuel hog. Of the 10 or so duramax owners I know in the area, all are complaining. The response from our local Rydel - Chevy General Manager was to purchase an aftermarket chip from "a guy down the road a piece". Is anyone else as frustrated with 15 mpg highway? Anyone interested in pursuing a class action to get a valid fix from GM? I'm at a point where I either get a factory fix, or God help me, I'm considering a Dodge and a Cummins ...

:mad:
 

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That would be all great, but there is no mileage listed on the sticker. So, I would think you would have a hard time going after GM. The only way that you would really have a leg to stand on is if something was listed on the sticker....even then, if you read the small print on the bottom, you would see that the upper and lower numbers are +- 5 mpg i believe. I'm sorry to hear about your problem though. I guess I am glad that I have the LB7 engine. When I bought mine, I didn't know anything about the LLY.
 

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I gave up on MPG :rolleyes: . And keeping the rpm's under 2000 :eek: going 65 mph :mad: takes too long to get anywhere :D . As long as I am getting the same or better than my 96 1500 am happy . On the stock wheels I was getting 20 mpg, but now who knows until do a recail. for the H2's.
 

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Durapig

I too am unhappy with the mileage of my Duramax. Another guy I know says he is getting 22-23mpg with his '03. My '01 Cummins got up to 20mpg and I left it running, a lot. Somebody better start making a 20-25mpg truck soon, I am unhappy with this power race they are having. I am checking into a new Cummins to see if there are going to be changes soon.
Another bummer about the Chevy, you can't shut the outside air off. If you are on a dusty road, driving by a hog factory, or driving through someones smoke from trash, you have to mell it and breathe it in. This bites, the Dodge you can shut it off. KY
 

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The fuel millage drop from the lb7 to the lly i dont think is gms baby go after the government and all there emisions bull$hit, my 05 with all the emissions stuff removed i get 16 city/town 20 highway and 15 towing my 6k horse trailer all at about 500rwhp

and just last weekend i avg. 12mpg towinga buddies 12,200lb trailer to ocean city and back @ about 400rwhp

All these mpg are hand calculated also as i dont hav a dic in my truck!

Later
Caleb
 

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Maybe us ZF guys have a slight advantage in the mpg department!:poke
 

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I think the stick helps becaus it takes less power to turn the trans, but other than that the gear ratios are very close on the top end!

Jon looks like your truck runs pretty healthy, hows the mitusa pump working?

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Caleb
 

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You can tell there is a constant load on the engine with the auto,but the ZF isn't for everyone:peelout!
 

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My 05' got 18MPG stock and 19-20MPG after adding a K&N. Then I got 22.5 with the banks six gun set on level 3.

My 06' got 15MPG stock, now it gets 11MPG after putting a straight pipe in and 20" wheels with 33" mud tires.

I took the lid off my factory air box and gained a lil over 2MPG! The truck gets 13.1-13.2 now.

Needless to say, I WILL be buying another Banks system soon!! I'l prob shell out $60 for a K&N first though.
 

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2ToneLBZ,

were all those numbers hand calculated? If not, I would not trust those numbers. I cannot see a programmer adding that much mileage. Also, I'm sure that your speedo is off with using the 33" tires and mud tires don't help mileage at all. I replied to a different post that you replied to....check out the tire calculator and make sure that you add the difference of tire size before figuring mileage out by hand. Also, just a word of caution on the K&N.....they let A LOT of dirt in the engine. Do a google on Spicer filter study online. You would be better to go to dieselplace.com to do that search....read up on that forum. Your stock filter does the best at filtering. If you think you need an aftermarket filter, go with the AFE....it is second best to the K&N.....unless you decide to go with the new amsoil filter IIRC.
All I can say is definately hand calculate you fuel mileage. If I didn't hand calculate mine and went off the DIC, I would be getting 24-28mpg. I get about 16-19mpg hand calculated.
 

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Yeah, everything was hand calculated accept my picking up 2MPG. That's just how much the DIC shows....I figured if it jumped that much, I gained at least that.

I calculated actual miles traveled divided by fuel used for the rest of it. But this WAS all highway miles.

The milage I was getting with the 05' was on factory tires also.

I don't know how much milage a programmer will add on the LBZ, but it damn sure can't hurt it!
 

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I just joined this forum because of similar problems I am now reading now. My mileage is horrible, and towing my 28' 7000 lb travel trailer I get 9 MPG. My fan clutch is engaged almost constantly while towing also, it was replaced by the dealer but it still does it. I've even had the fan clutch start roaring just driving down the road at 65 MPH with no trailer. I was really hoping that it might just be that it only has 13,000 miles and needed more time to break in. I guess I'm not alone with these problems.

God help me if I hitch-up my 25 foot flatbed. My mileage drops to 10 mpg!! Is anyone else as frustrated with 15 mpg highway? Anyone interested in pursuing a class action to get a valid fix from GM? I'm at a point where I either get a factory fix, or God help me, I'm considering a Dodge and a Cummins ...

:mad:
 

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After the dealer having my truck for four days, I got it back today with a "could not duplicate problem" because they don't have any trailers to pull with it. They claimed that GM told them they have "no previous cases of anyone complaining of fuel economy problems while towing, and no previous cases of any problems with the fan clutch engaged at highway speeds while towing". The only thing GM did say was that the truck was supposed to lose some mileage while towing. They also said that I probably drive too fast and too aggressively, causing it to get hotter and lose economy. This was insulting, as I always just hit the cruise control when I get up to speed.
What is really maddening is that I normally tow a 1000 pound trailer with anywhere from 400 to 750 pounds on it, and I go from 18 to 13 MPG highway pulling that trailer and the fan clutch constantly kicks in.
 

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After the dealer having my truck for four days, I got it back today with a "could not duplicate problem" because they don't have any trailers to pull with it. They claimed that GM told them they have "no previous cases of anyone complaining of fuel economy problems while towing, and no previous cases of any problems with the fan clutch engaged at highway speeds while towing". The only thing GM did say was that the truck was supposed to lose some mileage while towing. They also said that I probably drive too fast and too aggressively, causing it to get hotter and lose economy. This was insulting, as I always just hit the cruise control when I get up to speed.
What is really maddening is that I normally tow a 1000 pound trailer with anywhere from 400 to 750 pounds on it, and I go from 18 to 13 MPG highway pulling that trailer and the fan clutch constantly kicks in.

Well, it sounds like the LLY fan clutch is pulling down the mileage. I have towed light a few times and only lost about 1 mpg. that was towing a pop-up camper (probably no more than 1000lbs). I was not nice to it either....I would always go WOT when passing someone since we have 2 lane highways here in Alaska. I do have the LB7 engine and I was running my programmer at 45 hp setting....I got 18mpg going from Ninilichik to fairbanks....about a 600+ mile trip.
 

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Some food for thought, I did not buy my 04.5 lly for fuel economy even though I am getting 20-22 MPG Highway no load(Hand Calculated matches perfectly the DIC). Pulling my 12,000 lb travel Trailer I've averaged between 8-14 MPG depending on hills, wind, etc. I have only added an AFE Stage II and I am currently going to start programming my truck with EFILive, but not for fuel economy. My brother has a 02 Cummins (12 sec 1/4 mile)all decked out and he is more fixing than running with up and down fuel economy. I don't want to be in the same situation. I want the power at a reasonable cost, economy is second.:rockin
 
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