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Discussion Starter #1
I need some input for my lly to improve my mileage. Your recommendation are appreciated. Here is the specs and upgrades that I have done thus far on my truck. Please remember as you reply that I'm not into racing and any modifications that I preform will be to improve mileage only. My truck has all the power that I need for pulling my 11,500 lb 5th wheel and mileage is my only concern. Pulling my 5th wheel at 65mph on flat terrain I average about 9.5 to 10.0. Empty highway I get 18,5 to 19 at 70mph. My truck is faithfully serviced and maintained. I clean my K & N every 5000 miles and fuel filter every every 10,000 miles and run Amsoil synthic. My truck is a 2004 GMC 2500 HD lly 4x4 extended cab with 96k

Upgrades are as follows:
Banks Ram Air with super scoop for cold induction with K & N filter
Superchips Fastpaq 2855 set in tow mod ( 80 hp gain)
285/75/16 Michelins with speedo reset for these size tires and mileage accuracy readings
Lucus fuel additive is used regurally in each tank fillup
Amsoil synethic oil

I've checked the electric fan and it only engages under heavy long pullsand when it does engage its never for more than 30 seconds or so. Engine temps and tranny temps run in normal ranges.
This duramax is in very good condition and needs nothing mecahanically that I'm aware of. Ive read about many additional upgrades that I can do to improve fuel mileage and if I added everything that says it will improve fuel mileage, I'd have a small fortune invested in upgrades. Every upgrade that I've done thus far has helped fuel mileage in small increments. I read of owners that say they are getting 22 to 24 mpg with their Duramax's and I question if thats a lot of hot wind or the truth.Thanks in advance for your help.
 

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exhaust
 

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I'd recommend getting an afe mouthpiece or an lbz piece at least, the stock piece is super restrictive and you will gain from this alone. Also a straight flowing exhaust will help, and keep your egt's down as well.

I would also recommend a pcv reroute and egr block/delete for piece of mind. But that's just my 0.02
 

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First thing I would do is upgrade the mouthpiece to the AFE or LBZ like stated above ^^^

I believe just the mouthpiece will increase the HP by 20HP if not more.
 

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Mouthpiece is a big deal...
exhaust next with a downpipe
 

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=1 on MP. A 5th wheel tailgate will get you 1/2 or more mpg if you don't mind running around with one. Better rear visibility too, so you don't run over thos pesky Priuses or Fmart Cars.... :)
 

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Mouthpiece, down pipe and exhaust.
 

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I'd recommend getting an afe mouthpiece or an lbz piece at least, the stock piece is super restrictive and you will gain from this alone. Also a straight flowing exhaust will help, and keep your egt's down as well.

I would also recommend a pcv reroute and egr block/delete for piece of mind. But that's just my 0.02
i did all this and it helped a lot, minus the mouthpeice cuz i have an lbz. but all of these mods are cheap and help out a lot with the longevity of the truck and mpgs.
 

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Discussion Starter #11
thanks for your help

Thanks everybody for your input and recommendations You've been a big help!!!!!!!
 

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^ No problem bud. With your banks intake I would look in to the AFE piece as opposed to the lbz piece since the lbz piece requires some trimming of your stock intake (which is fine when you have a stock intake, but i wouldn't want to cut up a banks lol)

You WILL notice a difference with it though, I promise you that. You're going to take off the stock piece and two things will happen. First you're going to be grossed out by the amount of oil in there and push a pcv reroute to the very top of your mod list, and second you're going to curse gm for ever putting such a flow- deterrent design in to use.
 

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x2 ^ the downpipe is just as bad...
 
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