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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ & LMM engine specific topics.

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  #1  
Old 06-08-2006, 09:19 AM
PJvH PJvH is offline
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Default How to improve MPG in '02 6.6L duramax???

I have an '02 Duramax in a Chev Silv 2500HD 4x4 crew cab running 15w40 Amsoil and Amsoil air filter with a Superchip set at Performance Tow (BTW...the superchip made NO difference in my MPG at any of the 3 settings) - getting 17mpg in town -19 mpg hwy. at 75mph (average).

How can I improve the MPG?
Has anyone tried a scoup in the hood to force air in or a bigger exhaust to reduce back pressure?

Thank you in advance for your help! PJvH
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  #2  
Old 06-08-2006, 10:38 AM
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Mark Rinker Mark Rinker is offline
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Talking

Grow wings and only drive into the wind.
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2005 GMC Yukon Denali 6.0L gas (hey its paid for)
  • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW
  • Total GM diesel miles to date : ~950K
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  #3  
Old 06-08-2006, 10:50 AM
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More Power More Power is offline
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Arrow Drive slower....

That's a good one...

Install an EGT gauge (pre-turbo pyro installation), then alter your driving habits in ways that keep the EGT's at or below 600 degrees... You'll see a significant MPG improvement.... In my truck, that's about 55-mph on flat highway with no winds...

Jim
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Old 06-08-2006, 11:18 AM
SoTxPollock SoTxPollock is offline
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MP I know your right, but I think I would go nuts if I tried driving across the country or across Texas driving 55. Ain't goonna happen.

PJvH, I don't think either of those items would help mileage. Its all about getting the most out of the fuel your right foot in demanding and keeping weight and wind resistence to a minimum. Easy starts accelerate slowly, let the TC lock up before shoving down on the petal so that slippage is minimized.Also one of the most overlooked things is to not back off the accelerator too quickly. Try not to use the engine as a brake, just start easing back slightly and glide down in speed. I think your mileage is pretty good for the speed. Oh yeah drive 55, Noooooo Nooot Tttthhhhaaaatt Ssssslllllloooowww..

Add about 5 more pound of air in the tires also helps. Doesn't hurt the tires any either, I just turned 80,000 miles on the original Bridgestones that came on the truck this morning.
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  #5  
Old 06-08-2006, 12:44 PM
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I think it would be a good exercise to aim for 600 degrees EGT, and then do everything possible to the truck and driving habits to raise MPH. Of course, tires, external accessories, weight, driving habits and other factors can all be tweaked to raise MPH, while maintaining the 600 degree limit.

It could require a a change in driving techniques to maximize fuel economy.

Jim

Last edited by More Power; 06-09-2006 at 02:15 PM.
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  #6  
Old 06-08-2006, 04:06 PM
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Slowing down to only 65 average would likely bring your mpg up 1 mpg.

Have you considered a tonneau cover to smooth out airflow? They look nice, too.

A front air dam and lowering your front torsion bars (and getting a re-alignment) might cut air under the truck.

Run all synthetics - engine, tranny, transfer, diffs.

Road tread tires, not mud/snow traction types.
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2005 GMC Yukon Denali 6.0L gas (hey its paid for)
  • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW
  • Total GM diesel miles to date : ~950K
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  #7  
Old 06-09-2006, 01:56 PM
PJvH PJvH is offline
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Default PJvH

Thank you all for your helpful replies!

I am running full sythetics throughout, Michelin 265-75R-16 LTX/MS (recalibrated to non-stock tire size by SuperChips) w/ 55psi front and rear, just aligned, with empty bed. I start slow and look ahead to minimize using brakes by easing up on throttle when distant light is amber or red. I occassionally use Tow Haul to slow the vehicle - it increases rpm but at no cost to fuel consumption (I think) Camper shell or open bed I get the same mpg. I guess the most useful thing is to drive slower! - but in Atlanta area you get run over under 70!

Thanks again friends!
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Old 06-10-2006, 11:55 PM
akrockhound akrockhound is offline
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Default you are not doing all that bad

My '03 numbers are 20 hwy and 17 city, summer, #2 fuel at 65MPH hwy.

I agree that your not doing all that bad at 75mph.
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  #9  
Old 06-12-2006, 10:21 AM
nlp nlp is offline
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I have the same truck (mine has 72K). I get the same mileage as you. I get 16.5-17 city/18.5-19.5 hwy depending on speed. At 75 mph, I'll get 18.5 at 65 mph it's 19.5.
I have Michelin MTX 265's and run them at 55 psi front/50 psi rear when unloaded. Other than running synthetics, there isn't anything else you can do. Mileage has everything to do with weight, coefficient of drag, but mostly speed.
Not much you can do about weight and coefficient of drag. Reducing speed helps but I'm unwilling to drive 55mph...
A bed cover helps a little with drag. Driving with your tailgate down INCREASES drag and hurts mileage, it goes against convention, but it's been proven in tests.
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  #10  
Old 06-12-2006, 11:25 PM
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I run more air pressure in my Mich 265's, 65-70 front and 55-60 rear when unloaded. The truck handles better with a little more pressure and the tire "squat" looks correct. More pressure should decrease rolling resistance.

Jim
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