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Author Topic: Diesel mods Topic is locked Back to Topics
#12#_Hamrdwn
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El Paso

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Joined:May 2006
Message Posted: May 15, 2006 2:34:54 PM
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General query for diesel owners. Mine is an 03 GMC crewcab 2WD shortwide with the Duramax with 38,000mi. The onboard system says i'm getting 16-17 around town and 17.6 on the hiway at about 80-83mph. I'm looking for experiences on mods to help mpg and low end pep. It sounds like an air intake system, exhaust and low hp chip will yield the best results per $ spent. Please tell me about your experiences.
First post. Thanks for the insights.
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BioD
Veteran Author Detroit

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Joined:Jun 2006
Message Posted: Jul 28, 2006 8:13:24 AM
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I own a 2003 6.6L w/Allison 5 spd, ext cab short bed 4whd. I recently changed over all the lubricants in the drive train and the engine to full synthetics. Most noticeable is the temperature drop, about 10*F on the motor and transmission temps. The truck is currently getting 21-25 mpg (prior to change out). I typically drive 55-60 MPH. I changed out the lubes at 24,000 miles. I have also replaced the stock oil filter with a bypass system to improve the life of the oil in the motor.
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mahatma171
Champion Author Pennsylvania

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Message Posted: May 29, 2006 12:24:15 AM
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First of all, if you can help it, slow down!! That should be good for about 5 mpg.

Your diesel needs air. Then, it needs a way to get rid of the air. All diesels love air, thats why all the newer ones run turbos. Get rid of the stock air cleaner and look at some of the K&N products as a replacement.

On a turbo engine like that, a 4" exhaust from the turbo back will do wonders.

If you still have the 245/75/R16 tires that I think come standard on those trucks, consider going to a 235/85/R16. It is a taller and ever so slightly skinnier tire. Higher gearing, less road drag. I wouldn't be surprised if you got another 2 mpg.

My personal everyday diesel is a classic. 1986 Chevy Blazer Silverado 4x4 with a 6.5 liter natural diesel. I have rebuilt the 700R4 transmission and added a new lightweight early-lockup torque convertor from DAYCO. I also installed a dual 3" exhaust (I don't have a turbo to worry about so I can run duals no prob) and put in a K&N air intake system. This truck is getting 18-19 mpg in the city and 25 on the highway. It won't out-pull your Duramax but it sure is a comfortable and cool ride, nice little personal sized diesel. And it pulls my 21' long Bayliner boat with ease.

[Edited by: mahatma171 at 5/29/2006 12:27:10 AM EST]
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