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Sierra 3.0

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  1. I have also had this problem. I have almost 20,000 miles and have had the oil changed 5 times. I have always called the dealer, explained I have this new truck with the 3.0 and that it takes the special new oil. I then ask if they have it. They have been out of the oil several times so I had to wait for an oil change. Once they told me they had it in stock. I showed up an hour later and they took my truck back and they informed me they did not have the oil after all. They had removed my oil cap and forgot to put it back on. I found it under the hood in the recessed compartment on top of the grill. It's hit and miss with the oil situation!! I have always changed my own oil in all my vehicles but it makes no sense on this truck. The oil change at the dealer cost the same as if I were to buy the oil and filter alone. I have searched online and can not find it cheaper in order to save money by doing it at home.
  2. I have been keeping track of almost all fill ups with my 3.0 Duramax and hand calculating the mileage. I currently have just over 19,000 miles and wanted to post an update. So far for my total average mileage with mixed driving (city, highway-Non-Towing) I am getting 24.91 MPG. I have also had no issues with the truck. I have towed with the truck and forgot to record some fill ups in case you see the discrepancy of miles on the truck VS total trip mileage. Date Gallons Diesel Trip Mileage MPG Truck Computer April 28th 18.768 436.1 23.24 22.1 May 5th 20.674 492.7 23.83 22.7 May 15th 17.823 470.3 26.39 24.8 May 24th 19.409 472.9 24.36 23.6 June 2nd 20.547 537.1 26.14 25.1 June 19th 19.532 509.8 26.10 25.5 Jul 1st 19.199 456.4 23.77 22.5 July 8th 21.077 527.2 25.01 23.6 July 12th 13.174 322.2 24.46 23.3 July 16th 21.305 459.4 21.56 20.6 July 24th 22.092 543 24.58 23.30 July 29th 21.294 535.6 25.15 23.8 Aug 14th 19.829 455.8 22.99 22.5 Aug 28th 20.917 481 23.00 21.7 Sep 11th 19.505 476.1 24.41 23.6 Sep 20th 20.909 506.7 24.23 23.5 Sep 28th 19.446 512.2 26.34 25 Oct 14th 21.933 583.8 26.62 26 Oct 20th 21.162 588 27.79 26.8 Oct 31st 20.059 495.3 24.69 24.3 Nov 8th 21.805 550.6 25.25 24.6 Nov 16th 20.981 554.8 26.44 25.9 Nov 21st 14.668 380.7 25.95 25 Nov 25th 21.815 550.3 25.23 25.4 Dec 1st 22.846 576.5 25.23 24.8 Dec 18th 20.696 506.5 24.47 23.8 Dec 28th 20.659 533.1 25.80 25 Jan 21st 22.342 544.3 24.36 23.9 Totals 564.466 14058.4 24.91 24.025
  3. Mine did the same when it was brand new. Gas mileage began going up as it broke in. Now I never get any less than 24 MPG on a tank of gas. Give it a few thousand miles. It will come around.
  4. Take it into dealership. They will fix it.
  5. I beleive that GMC is having quality control issues at assembly. I have heard many instances of oil leaks, bad engines etc. I bought my 2020 3.0 1500 and it had an oil leak from the factory. GM better get this under control!
  6. I have been trying to keep track of my mileage each time I fill up. I posted my towing mileage a few weeks back and thought I would post my hand calculated mileage for non towing, everyday driving along with what my computer reads. Everytime I fill up I set the pump to fill then when it shuts off I wait 30 seconds and let it run again until it shuts off. I then take a picture of the gallons on the pump and my trip odometer for that tank. I then reset my trip for the next tank. I commute to work M-F and then drive the family around on weekends. My commute is approximately 30 miles one way and I drive a mix of highway/back roads and in the city. For those who are curious on what you might expect if you purchase a GMC with the 3.0 diesel here are the results. I kept track of 4224.7 miles of general driving with my truck. I used 170.203 gallons of fuel. My hand calculated mileage was 24.82 and the trucks computer read 23.69 MPG. I have about 8200 miles on my truck as of today. Attached is the spreadsheet with all the details. Sent from my SM-N950U using Tapatalk
  7. I do not have any specifics on my regens but it's doing it at least 2-3 times on each tank. I'm a little disappointed in this as the fuel mileage goes down significantly each time. If these did not have the emission controls the mileage would be incredible. I have not seen my average to be anywhere near 29 MPG on the highway going 70 MPH. My average mileage so far has only been around 24-25 MPG and the faster I go on the highway the lower it gets. Then when regens hits I get 20 MPG.
  8. I can confirm. I had mine done about 2200 miles ago. I pulled a camper for the first time and, wow, it used a lot of def. Now back to normal driving and it's still more than it was. I'm guessing the update solved an emission issue with not running clean enough?
  9. There is nothing to worry about. The truck likely hit its first diesel particulate re-gen and the exhaust components get really hot causing the smell. I have had the 3.0 liter and now have around 7000 miles. Mine did the very same thing and smelled awful. My old truck, a 2007 Chevy Duramax, also had a DPF and its first few regens smelled the same. It may smell like this for the first few regens but it will eventually get better and you wont notice it anymore. Congrats on the new truck! I'm very happy with mine!.
  10. Is the ATV pushing against the tailgate? If so you may have to get 2 persons and each person push in on the outside of the tailgate near the latches and then try pushing the button to see if it will release.
  11. No, I did not measure the drop but I could see it. The steering felt fine and not loose. When I picked it up I just used the same setting he had for his F-150. I did tow a camper with my 07 Duramax. We took a trip to Texas and went across the entire state and along the Gulf Coast. I seem to remember getting about 10 or 11 MPG for that trip but it was a lighter trailer than the one I towed last week and the computer usually overestimated my mileage instead of underestimating it. I hope you guys have a great vacation and I know you will enjoy the pulling experience!!
  12. My engine makes a more pronounced diesel noise occasionally. I especially noticed it after removing a heavy trailer and the first few miles unloaded it makes more noise. I would not call it knocking though.
  13. I filled up before I left. I used about 15 gallons during the trip. Just FYI...I hate DEF. Its not too bad if you fill up at a pump but if you use the jugs it overflows and leaves nasty white crystal mess all over your truck side. It also makes your hands all sticky.
  14. That's been very consistent with regular driving as well. The hand calculation is always better than the computer.
  15. I just got back from vacation and thought I would let anyone who wants to know what it was like to tow with my 2020 GMC SLT 3.0L diesel. I will include my towing fuel mileage for the trip. I purchased my truck on April 15th of this year. I had an initial build quality issue with it as it was leaking oil when I brought it home. Turns out there was an improperly installed gasket and seal leading from the oil pump to the engine causing the leak. The engine leaked 2 out of the 7 quarts of oil before the problem was found. The dealership fixed the issue and I have been trouble free since. The truck has 6700 miles as of today. Overall I'm very happy with the power/smoothness of the 3.0 and 10 speed transmission. In everyday driving it's a really nice combo. I know this engine is an unknown in many ways but I wanted better fuel economy and after an abundance of research I took the gamble on the GMC. I really like the look of the truck and I have wanted a 1/2 ton GMC for some time. I'm coming from a 2007 new style Chevy 2500 6.6 Duramax. My average MPG for the 166,****** miles I drove it was right at 14. I kept it stock and used it for occasional towing but mostly commuting. I had very little issues with the truck other than rust that developed over the rear wheel wells. Last week my family and I took a trip from Missouri to Lake Superior and Lake Michigan on the US side. We left on June 20th and got back on the 28th. We used RV Share to rent a travel trailer in Iowa on our trip to the lakes. The trailer was a 32' Keystone Bullet 277BHS, GVWR 7600lbs. I did not weigh the truck and trailer but I'm sure the trailer was at least 8500 lbs with our gear etc. I did use a weight distribution hitch that was provided by the owner. It was set up for his Ford F-150 and not for my GMC. I'm sure I could have adjusted it to better control my rig but it worked OK. The only issue I had towing was bounciness on rough roads. If I were to own a travel trailer I would add air bags to the rear of my truck and make sure the weight distribution hitch was completely dialed in. The truck did a great job hauling my family of 4 and the trailer. I had plenty of power and I did not feel like I needed more engine at anytime during the trip. The overall comfort in the front seats was fine for long periods of time but the rear seats are too hard and too straight up and down to be comfortable for a long trip. My wife suggested GM could add a slide to the seat bottom so the seat bottom would slide a short way towards the front seats creating a reclining affect. Everything else in the truck worked well. The trucks GPS was slightly below par compared to google maps but it did get us from destination to destination and was OK while navigating. Using my voice to search for addresses etc did not work well. The voice calling also does not work well when trying to get a contact to pull up from my phones contact list. GM needs to fix this. I hand calculated my mileage at every fuel up using my trip meter and the gallons needed to fill the tank. I allowed the pump to run until it stopped then waited 20-30 seconds and ran it again until it stopped. I have attached a pic of the spreadsheet along with the trucks computer read out. In all I averaged 11.73 MPG over the entire 2039.2 miles of towing the trailer. The trucks computer average was 11.31 MPG. I hope this helps anyone who is curious about this truck and engine combo for towing.
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