Probably a good idea. I'm at around 3000 km and oil life is still at 75%, the DEF level has gone down by 1/8.

It depends on how soon your dealer will let you come in to have it changed to use the free ones. If it was mine I would get it done at 1,600 km. Then go by the OLM from there. I like to get the factory fluid out and any machining material that might be in there out. Do you have to? No but I feel better.

The first 2 oil changes are free at the dealership.

I did the first one myself at 5,500 miles a couple weeks ago. I did pickup 1mpg it seems using DexosD 0w20 and a upf66r filter

I'm going to do mine early. Just now at 700 miles. I will probably change at 2,000 miles and then go off the computer. Seems like cheap insurance.

I've got about 2,000 km on mine and oil life monitor shows 85%. The owners manual doesn't mention anything special about the first oil change other than the regular 12,000 km interval. What's the general consensus for a reasonable amount of kilometers till first change?

I went from a 2018 Sierra 1500 5.3 SLT to a 2021 Sierra 3.0 AT4 two weeks ago. The 2018 had a Warn Ascent replacement front winch bumper w/Warn Evo 10s. I kept the winch when I traded it in, expecting to put it in a replacement bumper for the AT4. I can only find front bumpers for the 3.0 duramax w/o a winch mount. I can’t even find a simple 2” receiver mount to use w/a cradle. I don’t know this for sure, but I think the issues are a lack of space due to intercooler location and airflow to intercooler. Getting the diesel was more important than lack of bumper availability for me. https://www.addictivedesertdesigns.com/2019-gmc-sierra-1500-front-bumpers

Stayed with stock tire size, 265/65/18's currently am running the Fortitudes for the summer. 26K on truck now and am still very pleased with it.

What tire size did your truck come with and what size did you go to? May may need a calibration if you went to a larger size tire. The larger size will not only mess up your MPH, but also you MPG and shift points. If you went up, I would recommend this. It may get you those MPG's back.

I have not, but I'm looking at the 6112's for the front and 5100's in the rear. The front end of my RST CCSB is just a little too squishy for me. Feels more like jumping on a pillow over bumps...like an old Cadillac kind of bobbing.

Post pics and total height please.

I agree with you, but shouldn't the first oil change be free?

2020 AT4 3.0, Traded in my 2019 Tahoe premier for it last September. I absolutely love it! The mileage is better, the 10 speed is smooth and it’s got more jam than the Tahoe(5.3) So far I’ve had it levelled, backflip tonneau installed, rear under seat storage box and swapped out the antenna for the Ronin stubby. I’ve plasti dipped the badges and will be doing the fog light bevels and mirror caps with white vinyl on my next days off. I don’t mind the rim design so I’ve been going back and forth on new rims or just powder coating the stock ones. The Duratracs are okay but I will definitely be going with something else when it’s time to replace them. We get lots of salt up here because of the winters so Rust check will be happening before another winter comes. Waiting for S&B intakes to come back in stock and doing research on 2” lifts and better shocks. And I’m really wanting a set of Bodyguard bumpers (front and rear) but with the exchange rate it’s not happening now.

I have notice on my 2021 silverado 3.0 duramax that the def consumption really increases with trailering. I have hauled a 7000# travel trailer 2000 miles and experienced consumption at a rate of around 2.5 gallons per 400 miles travel. My mileage while hauling is at 12.5mpg. This is half of my usual mpg as when i am not pulling a trailer i average 24 to 29 mpg. A month before i traveled 3000 miles not hauling and went through less than 3 gallons of def. The other problem i have found is that i get warnings of 779 miles remaining before i run out of def but the def green gauge shows full. Any idea if i have a problem with these issues? Any recall notices?

I agree with following the advise given above for break in but i have always felt that the oil is the center of care for the engine. It suspends all contaminants in the lubrication side of the engine. I always change oil earlier than recommended. I understand some engines have break in oil and i leave the oil in at new until i hit 3000 miles. At that point i change the oil and filter and install synthetic oil. By the way you need to use dexosD, yes dexosD oil in this engine. The reason for this early change is that a new engine has junk in it with sealants that fall off joints or metal shavings, or other lubricants that were installed with bearings or metal rust preventative to prevent new parts internal to the engine from rusting before they are installed into the engine. And let us not forget about dirt and dust. So after 3000 i want fresh oil in and contaminated oil out. I believe it is a safe thing to do and cheap even at the cost of this expensive oil.

I just completed a draining of the fuel filter to clean out some water in the fuel. It was scarey but really easy in the end. You need a #40 torx driver to open the drain on the cartrifgmmdge housing. It is located in the bottom of the housing. The owners manual supplemental instructions. Once you have done it you will realize it is really easy to do. Also when you change the fuel filter you will need a 6 point 36mm socket to remove and re install the filter cartridge.

Really, i find the requirements for DEF to be pretty clear as a mixture of 32 percent urea to 68 percent distilled water. There is no real reason for extreme high prices versus extreme low prices unless it has been tampered with or just a scam. Just by a known manufacture and you should be ok.

I don't know for sure, but it might have something to do with the active shutters behind the grille.

Hi everyone. Have a 2021 Silverado 1500 RST Dbl Cab with 3.0 Duramax on factory order. Have Bilstein 5100's to use when the truck arrives to replace the Rancho's. None of our area dealers have any truck inventory on hand to measure the Duramax ride height versus the V8's but was told the diesel sits about .5 inch lower. Has anyone installed the Bilstein's to level their 3.0 duramax truck? If so did you set the fronts at 2.0 or 2.5" ?? Also not sure if I should be ordering a 1" rear block kit or not. Our previous truck required higher blocks after a 2" top leveling kit was installed. Any advice greatly appreciated!!

I've only ever used the Walmart brand with no issues.

I posted this in the general forum before I knew there was a special diesel club! I've been trying to research grill guards (and a bump bar if pushed to that). Most of the ones I found say they are not for the 3.0 diesel. I can't quite figure that out unless it has to do with the block heater connector by the driver's side tow hook. I'd like to hear from anyone that got one installed and which one it was. Thanks!

I think the manual (not diesel supplement) has the procedures, but from memory it's probably something like no speeds over 55mph, don't drive at a constant speed, no towing for first 500 miles. To be honest, I've been a bit of a skeptic on engine break in for modern cars; I've had cars up over 100k mileage that I drove like a beast from day 1 and cars that had so many problems in the first 1000 miles while driving it like a baby (I'm looking at you Ford!).

Hello fellow 3.0 members: I am new to this forum and club so please have some patience with my inexperience. I am buying a 2021 AT4 next week with the 3.0/10 speed powertrain. I have owned a 6.6 LBZ Duramax in the past so not a diesel newby. I am driving 250 miles to an out of state dealership to get this truck. My question is: what advice can you provide on the proper break in procedure for this powertrain? The first miles on this truck will be 250 miles of interstate driving from Pocatello ID to Butte MT. I plan to use the truck to tow my camper this summer so I need to get it broke in for trailer towing pretty quick. Any thoughts will be appreciated. Thanks

18,000 km now on Denali, no shift issues at all. Still smooth like a Molson Golden.

Traded my '20 High Country (w/18K miles) in on Jan. 30th for a '21 AT4. I've noticed that the trans "sticks" or "hangs" b/w 1,600 & 2,000 rpms in all driving environments (flat, minor grades & hills, etc). I have to play with the pedal to get it to shift & I don't ever recall my "20 HC doing this. It was rock solid & was smooth as butter....never noticed anything with it. Took the AT4 into the dealer to have it checked...."it is fine, no issues with it, it's in spec". It seems to be getting a little better now that I have 4,9xx miles on it but it still hangs. Curious if anyone else has had this experience?