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Open Roads Forum  >  Tow Vehicles

 > 2004 chevy Duramax LLY's horrible MPG

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fish58

florida

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Posted: 05/04/12 11:41am Link  |  Print  |  Notify Moderator

My 2004 Chevy Silverado 3500 gets only 12 mpg without towing and i drive like a nun.After doing some reading it turns out, it appears the the turbo inlet tube is restricted due to a necessary bend from the manufac. AFE makes an after market tube that supposedly allows 73% more airflow. Has anyone ever replaced this tube and were you successful in bumping up your mpg? Also, if anyone has added a chip to my model & year, what brand and how much improvement did it make? Any other suggestions to increase my mpg, I would love to hear some recommendations.

donn0128

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Posted: 05/04/12 11:48am Link  |  Print  |  Notify Moderator

When I had a LLY I saw close to 20 non towing. I suspect you have injector issues. Fix that and your milage should go up a lot.


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bartlettj

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Posted: 05/04/12 11:51am Link  |  Print  |  Notify Moderator

More airflow doesn't usually increase MPG, in fact it often hurts it because it allows the engine to make more power. It sounds like you probably do need a fuel injector repair.

bob213

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Posted: 05/04/12 11:55am Link  |  Print  |  Notify Moderator

I replaced mine. Not for mileage but for turbo and engine cooling. Really did not see an increase in fuel mileage. Mine was an 05'. I agree that you may have other issues.

JKrussow

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Posted: 05/04/12 11:59am Link  |  Print  |  Notify Moderator

I have the AFE turbo mouthpiece and a Bank IQ system. The mouthpiece improved mileage a little but if you are expecting to go from 12 mpg to say 20 mpg it's not going to happen. I got the mouthpiece as part of my plan to lower incoming air temps to prevent overheating. If you have been seeing the 12 mpg for quite a while (1000s of miles) then it may be the truck. But if the mileage has just started to suffer I would look into Donn's suggestion and have the injectors tested.

I get 11 to 13 mpg towing and 15 to 17 empty. Banks system is set for economy when empty and to power level 4 when towing. Either way I do try and set speed records with; I'm driving no faster than 60 mph towing and 65 empty.


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the bear II

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Posted: 05/04/12 12:05pm Link  |  Print  |  Notify Moderator

You may find some help at www.dieselplace.com
Look for the forum aimed at duramax engines or Chevy light trucks.

ScottG

Bothell Wa.

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Posted: 05/04/12 12:07pm Link  |  Print  |  Notify Moderator

I'm curious, do you have to crank the starter longer now than you used to? That's one of the early signs of injector problems.


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Turtle n Peeps

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Posted: 05/04/12 12:11pm Link  |  Print  |  Notify Moderator

donn0128 wrote:

When I had a LLY I saw close to 20 non towing. I suspect you have injector issues. Fix that and your milage should go up a lot.


^^^ This.


~ Too many freaks & not enough circuses ~


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outside the fire"


NewsW

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Posted: 05/04/12 12:53pm Link  |  Print  |  Notify Moderator

Need more specifics, mileage, maintenance, etc.

If it is a DRW, 12mpg may not be that unusual.

Winter fuel and cold weather use also gets a lot less mileage.

M GO BLUE

Southgate, MI

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Posted: 05/04/12 12:31pm Link  |  Print  |  Notify Moderator

My 2005 I still get 18-19 non-towing....




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