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Chevy Silverado and GMC Sierra Duramax Fuel Mileage

620 messages,  Last post on Dec 15, 2012 at 3:45 PM

You are in the Chevrolet Silverado & GMC Sierra Forum.

What is this discussion about? Chevrolet Silverado 2500HD, Chevrolet Silverado 3500, GMC Sierra 2500HD, GMC Sierra 3500, Diesel, Fuel Efficiency (MPG), Truck

Messages Page 60 of 63

#584 of 620 Re: DURAMAX FUEL MILEAGE [keygmc] by kula_jon

Mar 27, 2011 (6:41 pm)

Replying to: keygmc (Jan 20, 2011 2:11 am)
Hi, I bought the H&S XRT Pro package with the cold air intake and DPF delete pipe. I just unplugged my EGR and air intake valve connections. I just switched to "hot". I have not seen the gains that you're speaking of, up to this point. I was getting 13.3 and it went to 14.4 but that's all. Am I missing something? I seem to have copied your setup (except I don't have Banks, I have S&B intake).I have a 08 2500 HD with the 6.6 LMM Duramax, extended cab, Allison trans, 4x4 LTZ. I upgraded so I could haul my backhoe. Since it's so dang slow I'm not hauling anything these days.
I'd appreciate any pointers. Thanks.

#585 of 620 Re: DURAMAX FUEL MILEAGE [kula_jon] by kacansas06

Mar 27, 2011 (7:10 pm)

Replying to: kula_jon (Mar 27, 2011 6:41 pm)
My quick reply would be that if you didn't replace the computer with one that can work with the stock system you bought the wrong computer. Banks, Edge systems and another all have the purchaser install a "Y" connecter under the hood in the main wiring loop between the stock computer and the engine. They also add an EGT sensor on each manifold. The cold air intake + the bigger intercooler + the bigger exhaust w/o obstructions is how you get to run power levels higher than 2 steps above stock. The upper 3 or 4 power levels are NOT recommended for a stock transmission. Stock Allisons of that year are capable of around 750 ft-lbs without damage. I found all this out for I exceed the GCWR of my truck by about 4,000 lbs when towing our 18,000 lbs of boat & triple axle trailer with us loaded out for a vacation in the bed and cab of our '06 Duramax which still can get 14 to 15 the way I drive it under load with the first 2 power settings. At stock I get 11 to 13. My installer did not disconnect any of the stock systems, just added systems onto the stock which quails more mileage and performance. I did this because I lost so much when 500 ppm fuel became unavailable after '08. My guess is that you have actually hurt your performance and perhaps endangered the engine and transmission. good luck with that.

#586 of 620 2011 Duramax,CrewCab,2500HD,long bed by jerryel

May 26, 2011 (9:13 am)

My fuel economy is 14.8 mpg empty according to the truck computer. My 02 Duramax got over 20 mpg empty and around 12 mpg pulling my travel trailer. I only have 1200 miles on the 2011 and baby the engine. I never drive over 65 and most of the time I drive 55 mph. I recently took the truck to the dealer for a diagnostic check and they couldn't find anything wrong? All the reports I have read state that this truck gets from 18 to 22 mpg on the highway empty driving at 65! Is mine just a lemon? or do I need to wait 5000 or 10,000 miles for the fuel economy to improve? My 02 Duramax had a Bully Dog chip set at "towing". It also had the 4" exhaust(no catalytic converter), an Air Raid air cleaner and the Air Raid air intake ring. I love the new 2011 Chevy Silverado but not the fuel economy....Jerry

#587 of 620 Re: 2011 Duramax,CrewCab,2500HD,long bed [jerryel] by hillsdale56

May 26, 2011 (10:18 am)

Replying to: jerryel (May 26, 2011 9:13 am)
Hi, enjoy your new truck. I have an 06, the best year for fuel economy. Your truck will do better as you drive it more. By the time you get to 5000 miles should get better. The dpf kills fuel economy, you will not get the same mileage as with the 02. On my truck, I'm gutting the catalitic converter, and installing a magnaflow muffler. May get like 27 miles to the gallon then. There is no emission test on diesels,, here in ny. Stock pipe is 3.25. I think yours is 7 inches. After you break yours in, contact diesel domination in montana. Check them out on your computer.

#588 of 620 Re: 2011 Duramax,CrewCab,2500HD,long bed [hillsdale56] by barrail

May 26, 2011 (2:24 pm)

Replying to: hillsdale56 (May 26, 2011 10:18 am)
hi hillsdale; when you say your gutting the catalitic converter, are you just replacing it with a test pipe and do you have to reprogram the onboard computer?

#589 of 620 Re: 2005 Duramax Fuel Mileage [aarongd] by jerryel

May 30, 2011 (6:23 am)

Replying to: aarongd (Jun 28, 2005 3:53 pm)
I owned a 2001 Silverado, 3500 HD dually with the 8.1/Allison. I owned a very large camper at the time(11 1/2 footer that weighed over 5000 lbs). My mileage when I carried the camper was 8 mpg and around 11 empty(at 75 mph){we lived in Nevada at the time}. When I towed and carried the camper my mileage was around 6 mpg(at 60 mph). The truck was very powerful but the fuel consumption was expensive! I have owned a 2002 Duramax and recently bought a 2011 Duramax and find the diesel is well worth the extra dollars for reliability and much better fuel economy.

#590 of 620 hey barril, whats up? by hillsdale56

May 30, 2011 (2:50 pm)

What I'm going to do isremove the cat, and run with a test pipe. I'm also removing the stock muffler. Installing a magnaflow. 28 inches long, 3.5 inches in and out. When I get it set up and drive for a while, I will let you know how my milage is. I'm going to bring it back to stock. Tune

#591 of 620 my results by hillsdale56

Sep 01, 2011 (11:36 am)

Hello everyone what a storm, upstate ny is a mess. Here are my results. After doing what I said I can get 26 to the gallon with a good grade fuel. I used 3.8 galllons to go 102 miles. City and highway mix use is around 6t00 miles per tank now. Filled to top of neck. Truck does not smoke at idle or while running. I'm happy with it

#592 of 620 MN, but anyone in California in this thread by bulldoggit2

Sep 11, 2011 (9:32 pm)

How do these modifications impact CA emissions tests at registration?

#593 of 620 Re: my results [hillsdale56] by barrail

Sep 12, 2011 (5:19 am)

Replying to: hillsdale56 (Sep 01, 2011 11:36 am)
May I ask, what modifications were made and to what year D-max?

Messages Page 60 of 63

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