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Chevy Silverado and GMC Sierra Duramax Fuel Mileage



  • hillsdale56hillsdale56 Posts: 15
    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.
  • barrailbarrail Posts: 27
    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?
  • jerryeljerryel Posts: 2
    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.
  • hillsdale56hillsdale56 Posts: 15
    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
  • 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
  • How do these modifications impact CA emissions tests at registration?
  • May I ask, what modifications were made and to what year D-max?
  • What I did was remove the cat and stock muffler. Installed magnaflow number 129909. Pipe is stock size. Truck does. Not smoke at idle or when running. Also have a tuner froom diesel domiination. Ruunniing 25 lbs of boost at 1600 rpm. Look into his tuner. Steve shellly s a good guy and kknnows what he's doing. My truck is a 06. 3.73 4wd hd.. now at 420 hp. To answer the post about california, I not familar wth your emission. Testing. Dooo they put a snffer n the tail pipe, use a mirror to look under the truck? Here n new york we don't have emiissiion testng on diesels
  • Looking for some advice here folks...
    i drive my truck about an hour each way to work daily, purchased this truck in may of 2011 and was thrilled to see it was getting 18mpg on the drive home! After having the truck a bit i put a soft tonnaue cover on it and immediatly noticed a drop in fuel mileage, to date the truck has been getting around 15.9-16.2 mpg. Wanted to improove mileage so we put cold Air intake system with K&N and did Exhaust with hypertech programmer on stage 2. mileage has not gone up at all since the updates :-(
    Any advice would be much appretiated!!!
  • barrailbarrail Posts: 27
    did you rely on the on board DIC to determine your mileage or did you divide gallons put in to miles driven actual.
  • coontie66coontie66 Posts: 110
    Back 1.5 years ago the check engine light came on so I took it to the local Chev garage... Five trips later they eventually installed a new turbo in the 06 Diesel Chev. The fuel mileage never returned to its pre FIX of nearly 21 on the road. Now its about 17-18 on the road.

    This week the check engine light came on again so its back to the Chev dealer. This time he says its a glow plug and the EGR/ERG pump and a dirty air filter. The truck went out of warranty in July this year based on years NOT mileage... it now has 45300 on it. During the discussion he told me that the new turbo that they put on about a year ago produces more boost than the factory model AND less fuel mileage. Not happy with that. At first the dealer wanted $1050 to fix my problem but when he was told I would trade it in first he decided to extend my warranty a BIT and cover most of the costs. My NEW cost is about $250. What I didn't tell him is my next attempt to buy a diesel PU would be a Dodge. Sure wish they were quiter.

    I will have to say this 06 Chev is rapidly approaching the top of my list of bad vehicles. So far the Chev Vega of 72 fame and the 80 VW Rabbit are on the top of the list with the 99 Ford diesel in 3rd place. This vehicle is catching up fast and could take 3rd place next year.
  • coontie66coontie66 Posts: 110
    About a year ago I had the turbo replaced on my 06 Chev diesel. I thought the fuel mileage had suffered and last week the local dealer told me tha the new turbo produces more boost and the miles is off about 3 mpg. Darn I didn't need more boost just more mileage.

    What to do??? My mileage is about 17---------------grrrrrrrrrrr.

    Mine now has 45K on it.

    Had it in for a gloplug and a ERG pump... warranty ran out in July but they covered both with a 100 buck payment. At first they wanted $1050 until I complained.
  • gmcustsvcgmcustsvc Posts: 4,251
    How has it been running, aside from the less efficient fuel economy?

    GM Customer Service
  • I have only really pulled one time with it since the new turbo and that was with my 12500lb camper. It did really fine.. I have not chipped it yet but its loaded with power.
  • cefloydcefloyd Posts: 1
    what kind of millage did you get pulling your camper i also have a 12500lb camper and I am looking at a 06 hd3500with a 6.6 or a F 350 super duty with a 6.0 and I know alot of bad stuff said about the 6.0 just checking my options
  • coontie66coontie66 Posts: 110
    I was getting 11 mpg pulling my camper before the turbo change... I have not pulled it since the new turbo unfortunately. Both of us have been diagnosed with cancer in the past two years and treated. I think we are fine now just waiting to get time to travel again.. I know that the mileage on the road without the turbo dropped about 2.5 mpg.
  • I have a vibration in my truck, back to dealer at least 9 times now, no fix, i have 2100 MILES ON IT and i am getting tired of getting the run round . is there a fix
  • gmcustsvcsarahgmcustsvcsarah Posts: 1,964

    I'm sorry to read that after making so many different trips in for this to be looked at there has not been a satisfactory resolution for you. If we can follow up with your dealership on this, please send us an email at with more information (your name/Edmunds username, phone and address, the last 8 of your VIN and current mileage, the name of your dealership, and number of times you've been in for this same concern). My coworker Christina will advise you further.

    Thank you for your patience, and we look forward to hearing from you,
    GM Customer Service
  • You might take it to a place that does over the road (the big semi's) tires and have them check tire balance. I don't think tires are covered under the warranty. Happy hunting.
  • I have 2007 chevy 4x4 dura max with a milage at about 12 miles per gallon. Was wondering if this unusual or not for that truck I was hoping for much better than that.
  • I am very disappointed after owning my dmax for 4 years and only having 22000 miles on it. I get 17.5 mpg empty. I pulled my dads camper to New Mexico this week and pulled it fine, but got 5.6 mpg both ways and it did not matter if I pulled 65 to 75 mph. I thought it was because I pulled it to mountains full of gas and water but empty on the way home and was not any better. The camper only weighs around 7000 lbs. called the dealer and they asked when I had changed fuel and air filters and how much the wind was blowing. The 6.7 Ford is starting to sound nice , although my dads 2012 duramax gets 12 pulling same trailer
  • Good afternoon nater37,

    I see you've checked in with your dealership on this; if you want for us to look into this further with you and your dealer's service department please email us the following information at your name and Edmunds username, phone and address, the last 8 digits of your VIN and current mileage, and the name of your involved dealership.

    Sarah, GM Customer Service
  • A lot of this kind of fuel mileage problem comes from the driving method. I believe your truck has a tachometer like my 2006. When you accelerate with a big load do not wind the engine to high, say 3000 to 3500, RPM for all it accomplishes is using lots of fuel. When I am towing I rarely let the RPM exceed 2000. When driving without a load I take the RPM at speeds under 35 to 2000 or so and after that take my time and keep the RPM below 1800. Think of it this way, that 6.6 liter engine is more than twice the cubic displacement of a 4 cylinder engine. 4 cylinders go to 3500 to 4000 RPM or more all the time for shifts. So divide that by 2 for the diesel and you get your target RPM ranges. I recently took a fishing trip with 21 ft boat loaded and the truck heavily loaded and made 24 mpg going up north and 22 mpg returning at faster speeds. Oh yes, these truck do not like being pushed to 65 or 75 while towing plus the trailer tires are usually rated for a Max speed of 55 to 65(look at the tire sidewall). I tow our big boat, 17,000 lbs at 13 feet high by 10 feet wide by 45 feet long triple axle, at highway speeds of 55 to 60 cruise and max downhill of 65mph. Doing that I get between 12 to 16 mpg depending on terrain.
  • I think that there are at least two things I would like to recommend as possible answers to your post.

    The first thing is that your Duramax is not broken in yet and probably won't be for another 30K miles. Patience!

    The second thing is that it seems to me that speed and MPG are inversely related. The faster you go after a certain point the worse the MPG.

    About 6 weeks ago I drove to Winston Salem 150 mile drive and kept the speed on 62 mpg and got 20.2 mpg that was when my 06 Chev just turned 50K. Prior to that time I was getting 17.8 MPG after GM replaced the turbo. The new turbo (probably what you have and much better they told me) actually reduced MPG about 2 and that was back 1.5 years ago. The Chev got in the 20 range when new but not after the new turbo until 6 weeks back.

    Some where you can find the power curve graph for OUR engine. See if you can drive where the power HP and Torque are at its maximum for a certain engine speed measured in revolutions per min. That number will be around 1750 RPM's and will be 60 and 65 miles per hour.

    Keep driving and it will just get better but don't expect it before the engine is broken in.
  • Find the sweet spot for your engine. I have a 2005 and 1700RPM is where it likes to be. My wife has a heavy foot and she never gets good mileage from the diesel; so I keep her in the Geo Metro as much as possible.
  • rbboydrbboyd Posts: 2
    I bought a 2007 Duramax a month ago and it was getting 15.9 mpg on trip home. I put the chip in it and my fuel dropped to 13.5 mpg. I pulled a small camper trailer approx. 400 miles and got 9.9 mpg. After I quit pulling trtailer just going back and forth to work I am still getting 9.9 mpg. That was with my H&S chip set on "Hot" and not getting into it. I have it turn completly off now to see what happens. I have new fuel filter. Truck has 20" rims & has 6" lift on it. Any suggestions?
  • How many miles and hours on the truck?? How wide is the tread patch on the ground of the tires? When you say "Chip" is it a controller with multiple programs or something that plugs into the data slot inside the cab? The units that plug in in the cab are notorious for causing permanent damage to the engines computers and to the engine components such as fuel injection system defaulting to maximum fuel or burning up the turbo or damaging engine sensors and since the program is no longer stock the trucks computers cannot tell you what went wrong! Last thing is Never, Ever tow with with any computer modification set to HOT since the engine will overheat in many ways that you can no longer know about due to the change in the computers. Good computers that work with the stock computers and do not change the warnings system or the gauge readouts cost quite a bit, on the order of $1500 to $2000, when installed properly. Anything cheaper are the ones that can cause significant damage to the truck. Do Not take it to a dealer, go to another shop that is qualified to work on the Duramax system for diagnosis.
  • rbboydrbboyd Posts: 2
    I bought the truck with 84,000 miles on it and it now has 92,000 miles. The hours on engin has been reset. My tire size is 325x12.5x20. I pulled a small camper trailer approx. 400 miles but had my H&S chip set on mild. The H&S chip cost me $1,400 and was installed by a shop in Baton Rouge, LA. that does after market accesseries. It is one you can change on the fly. I am thinking that the shop didn't set the chip correct on fuel. BTW they told me to leave my chip set in the "HOT" setting at all times. The mechanic said I would get mpg because it had the most horse power provided I drived normal & not racing. I have the after market exaust & I put in the K&N air filter. The shop is suggesting the "Cold air Injection" instead. Any suggestions? thanks! I am working a pipeline around San Antonio till after the first of the year. If we rain out I will bring to a shop.
  • I have disagree with the break in part of the comment posted I was told when I purchased a new chevy duramax it would improve as it broke in as to date it has 99186 miles on it and has done nothing but get worse and gm for sure does not have a clue what is going on they will tell you a bunch of bs but no logical answers I started at 21 empty 14 towing a 16000 lb trailer now I am at15.9 to 16.3 at best empty and 10.2 towing my 1500 lb boat one reason I know is the fuel is not worth a crap and gm could give a damn less about so looks like we are on our own
  • I agree with rajun55cajun. Break in of my engine seems to have made little difference in mpg. Tire size made the most difference. I replaced the stock summer tires with a wide all season that had a road contact width of 12" 1/3 greater than the stock after a year. MPG went down by at least 15% to 20%, 4 to 5 mpg. A year and a half later I changed back to a close to stock width of 8.5" and slightly larger diameter and recovered most my mileage loss. Since I have an '06 it is not built for todays 15ppm ultra low sulfur fuel and that has cost me about 2 mpg. So today I can still get into the mid 20's mpg unloaded at less than 60 mph but usually get about 21 to 22. Mixed in city driving is around 18 to 19 mpg. City only with no highway speeds I get 16 mpg. Living in MN I change tires for winter and that takes away another 2 mpg in the city and about 1 mpg highway. I was told by nearly every tuner manufacturer to never run the engine with a much higher than stock program for you may overheat the turbo and other exhaust components such as valves. I was told by many more people that own these to not try to push it to 65 or 75 mph when towing a trailer. My experience with the truck has taught me that 55 to 60 mph towing gets me better mileage and 75 drops it into the 6-8 mpg area which is less than half what the truck can get when towing. I will take 14 mpg towing 17,000 lbs over a little more speed which could ruin parts of the engine and transmission.
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