Ask the Car People.SM


Chevy Silverado and GMC Sierra Duramax Fuel Mileage

621 messages,  Last post on May 30, 2013 at 3:47 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 59 of 63

#580 of 621 Re: Help my milage [rgferri] by kacansas06

Mar 03, 2011 (1:07 am)

Replying to: rgferri (Mar 02, 2011 8:47 pm)
first question: is it a diesel??? If not that is about the best you are going to get. Crew cabs weigh a lot more. If it is a diesel then I recommend you decide if you like the acceleration more than mileage. Take it easy on the diesel and you will get better mileage. If that doesn't work then the next easy step is disconnect the batteries, causing a transmission computer reset and then drive it easy. The Allison tranny behind the Duramax is a learning computer for shift points and the more hard acceleration the less up shift and fuel savings. Also the faster you drive the less fuel savings from the engine computer and tranny computer. An '06 diesel is the best one GM has produced lately for mileage.

#581 of 621 Re: Help my milage [kacansas06] by rgferri

Mar 04, 2011 (10:12 am)

Replying to: kacansas06 (Mar 03, 2011 1:07 am)
thanks for the advice. Yes it is a diesel. I just purchased it used and the computer said 10mpg and after a few days of driving i brought it up to 11.1 mpg. i have only been driving it for about 3 days now. i am hoping it keeps going up from there. I guess i was expecting mileage like my fathers 2004 duramax. is it taking me longer to raise the mpg because it has been at 10mpg for so long. would re-setting the computer on the instrument panel give me a more accurate reading??? any aftermarket products you guys suggest??? the truck has 104,800 miles on it so i am not worried about the warranty.

#582 of 621 Re: Help my milage [rgferri] by kacansas06

Mar 04, 2011 (1:26 pm)

Replying to: rgferri (Mar 04, 2011 10:12 am)
Oh yeah, reset that stupid display. The DIC that you are getting your MPG stat from arrives at it's calculation from the float position in the tank and the throttle position which means your pedal position as you drive. It is horribly inaccurate and the longer you leave it the farther off it will be. Mine say 14.4 mpg right now because I haven't changed it all winter. Winter is when a diesel gets the worst mileage for a diesel engine is most efficient when the engine is hot. I do not know where you live but here in MN I not only have the "Winter Front" covers on the grill and bumper, I added cardboard from the radiator down in front of the tranny radiator plus I covered the 2 holes left open on the bumper for the tow hooks with cardboard. This winter has been really cold but my drivetrain temps have been good thanks to the block heater and all the covers. No tendency to overheat either even on the few days that have been in the upper 40's or 50. So my calculated mileage at the pump has been 17 to 19 this winter. Close to the lowest I have seen in 50,000+ miles. Spring through fall I get 20 to 22 city(with No load) and when I tow our 16,000 lbs of boat we get 13 to 15. It really matters how you handle the drivetrain. I moderately accelerate to 35 mpg then back off and let it shift to 4th and if needed keep accelerating easy to highway speed. Maximum economical speed is 65 to 67 mph depending on head wind. I can hear the engine start to work harder in 6th with the torque converter locked up somewhere around that speed. It is the complete lack of aerodynamics of the truck which is like shoving a large stack of bricks through the air. But the dash MPG estimate is always off by 3 to 5 mpg or more for me since I have a steep driveway that it has to climb. Also you do not need to idle the truck when you stop to keep it warm for it has a huge amount of fluids that stay warm quite awhile. If you need more advice feel free to let me know if you need my email addy. Oh and if you wish to "chip" your truck get a tuner that connects in the wire connectors under the hood. The ones that plug in inside are DANgerous. For mileage without a load the lower program settings add air to the engine with the higher power setting adding fuel and air. High power settings are for people who need or wish to show off the diesel power but they can easily damage a transmission. The Allison is the "weak" point in the drivetrain but it can handle as much as 15% more power if it is in good condition. To check that have the fluid changed for the external filter has a magnet in it to detect how well it is operating.

#583 of 621 Re: Help my milage [kacansas06] by rgferri

Mar 04, 2011 (2:23 pm)

Replying to: kacansas06 (Mar 04, 2011 1:26 pm)
Thanks a lot. Great help!!! I'm not an aggressive driver by any means, i just want to get better mpg. we never reset my dads in-dash mpg display and for some reason it always ready about 17 city and 21 highway. hopefully like you said with me resetting that mpg feature it will start to show more accurate readings. as for idling the truck, i usually don't let it idle......its garage parked so it doesn't get really cold even though this winter was one of the harsher winters Ive seen. I'm from Michigan by the way....sorry if i didn't give you that bit of info...ha ha so yea we have had a cold one this year as well, maybe not as cold as you guys but close enough.
 
Thanks again for all your input and info!!

#584 of 621 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 621 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 621 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 621 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 621 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 621 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.

Messages Page 59 of 63

To POST a message, please Sign In.

Advertisement

Browse by Category

Browse by Vehicle
   View All Vehicles

Browse by Board
Browse by Topic
View All Topics

Edmunds Community

Advertisement