Thoughts on purchasing a higher-mileage Duramax?

carguy79 · Nov 18, 2024

Curious to ask those in the forum who have bought recent model, higher-mileage Duramax vehicles. I am exploring purchasing a year-old Denali Ultimate (with Super Cruise) that has just over 60k miles; service records show religious maintenance, oil changes, fuel filter changes, no accidents, etc. My plan is to not to use as a daily driver, but rather for occasional longer road trips and towing a camper.

Any used vehicle comes with risk, of course, so I am not expecting it to be as new. For those who have bought with higher mileage Duramax of this generation, what types of issues should I potentially plan for? Any Duramax-specific maintenance items to be aware of with higher-mileage engines based on your experience? Other things I should consider?

Stbentoak · Nov 19, 2024

60K Miles is nothing on a diesel engine. I would have all the fluids changed on the vehicle as part of a prerequisite to buy. If everything else adds up and it is in good shape and a fair price, I wouldn't let that mileage stop me and all.

blackelky · Nov 19, 2024

If only we could find a way to legally delete the smog lol

ReaperHWK · Nov 19, 2024

60k high mileage? lol. That diesel is barely broken in.

Marky Dissod · Nov 19, 2024

Any halfway decent turbodiesel that fails to exceed 300,000 miles is an indictment of its previous operators.

carguy79 said:
... service records show religious maintenance, oil changes, fuel filter changes, no accidents, etc.

If the motor oil was changed every 5000 miles, good. If more often than that, so much the better.
If you address maintenance items slightly sooner than recommended, 300,000 miles should be easy.

Big Bad Allis · Nov 21, 2024

I year old with 60K miles is better than 3 years old with 60K miles. The miles will be mostly highway miles and not a lot of short operating trips. With the good service records, I would not hesitate one bit.

dbphillips · Nov 26, 2024

If it's a 3.0L and it wasn't a case of the owner dying and no one in the family wanting it, I wouldn't go near it. I was willing to let GM buy mine back as a lemon due to time out of service (turns out it didn't qualify), but the only way I'd sell it is if it had a known issue, even though I haven't been able to confirm the fix for oil loss.

TiGrayMSM · Nov 26, 2024

My take as fellow 3.0 owner (2022 Yukon XL) is to buy the newest model year you can, especially for the LM2 diesels (2021-2024 for the SUVs). The early LM2s do have issues, which I have confirmed after befriending the diesel mechanic at our dealership. Areas to look out for per the tech:

1. Early builds (2020-2021) are prone to oil leaks (rear main)
2. Early build LM2s are starting to come in for timing issues caused by timing chain stretch. This is a massive cab-off job. The tech said GM updated the chains with a new design in 2022 (maybe earlier?)
3. Oil consumption (there is a TSB for this, involves replacing the camshaft housing. Also early builds)
4. Coolant control valve. He has seen both LM2 and LZ0s coming in with this issue, but especially higher mileage LM2.

Per the technician, almost everything involving the LM2s is very labor intensive so he is wary of owning one outside warranty.

With about 70k on our 2022 now, this is what has been replaced that is diesel specific: All replaced under warranty (some of it covered by CPO warranty):

1. NOx sensor
2. DEF sensor recalibration (the gauge was wildly inaccurate when towing. The update has helped somewhat)
3. Oil consumption (heavy consumption for us when towing). We had the oil consumption TSB performed and so far results are excellent. But FYI, this job was billed at 18 hours!
4. EGR valve replacement and EGR cooler replacement due to coolant leaks.
5. Coolant control valve replacement (P1098)
6. Intercooler replacement (massive internal coolant leak)

On the plus side, doing a transmission fluid/filter change is much easier on the diesels. The gassers have a crossover pipe right under the pan. I was intending to keep the Yukon long term.... as we do for all our cars. However, in this case, I will make the decision when we are closer to 100k.

petethepug · Nov 26, 2024

Like the others said, 60 clicks is nothing on a diesel. Look at as it just had a long test drive. SuperCruise + diesel = dream drive. Snàtch it.

If the dealer offers any kind of lifetime oil change promotion or CPO warranty get that too.

Seamus · Nov 26, 2024

TiGrayMSM said:
My take as fellow 3.0 owner (2022 Yukon XL) is to buy the newest model year you can, especially for the LM2 diesels (2021-2024 for the SUVs). The early LM2s do have issues, which I have confirmed after befriending the diesel mechanic at our dealership. Areas to look out for per the tech:

1. Early builds (2020-2021) are prone to oil leaks (rear main)
2. Early build LM2s are starting to come in for timing issues caused by timing chain stretch. This is a massive cab-off job. The tech said GM updated the chains with a new design in 2022 (maybe earlier?)
3. Oil consumption (there is a TSB for this, involves replacing the camshaft housing. Also early builds)
4. Coolant control valve. He has seen both LM2 and LZ0s coming in with this issue, but especially higher mileage LM2.

Per the technician, almost everything involving the LM2s is very labor intensive so he is wary of owning one outside warranty.

With about 70k on our 2022 now, this is what has been replaced that is diesel specific: All replaced under warranty (some of it covered by CPO warranty):

1. NOx sensor
2. DEF sensor recalibration (the gauge was wildly inaccurate when towing. The update has helped somewhat)
3. Oil consumption (heavy consumption for us when towing). We had the oil consumption TSB performed and so far results are excellent. But FYI, this job was billed at 18 hours!
4. EGR valve replacement and EGR cooler replacement due to coolant leaks.
5. Coolant control valve replacement (P1098)
6. Intercooler replacement (massive internal coolant leak)

On the plus side, doing a transmission fluid/filter change is much easier on the diesels. The gassers have a crossover pipe right under the pan. I was intending to keep the Yukon long term.... as we do for all our cars. However, in this case, I will make the decision when we are closer to 100k.

We have a diesel Guru tech at our GMC. Great guy, has said most all you mentioned. The oil consumption is a baffle in the valve cover. They replace the valve cover. Only effects 20-21's within a certain vin code. Coolant valve is a complex piece which was bound to be a problem...and it is. Still not a reason to get a new truck. There will be a new improved version at some point no doubt. Our guru who isnt a fan of this motor said they dont blow up. He has only replaced one 3.0 motor. Bad from factory according to him. I have a 2021 3.0 w/ 42K on her in perfect condition. I have only had a leaking radiator a quality control issue he said. They crack and leak on a weld. I just had this conversation with him as I want to go the distance with this truck. He has heard of the timing chain stretch and has not seen one yet. Mind you other dealers and customers travel to have him work on their diesels. Sees alot of trucks. As far as GM trucks go the 3.0 is about the best out there. I know people are programmed to fear being out of warranty, but it cheaper to fix a 3.0 than by a new GM truck today. I am prepared to pay at some point but know its cheaper than doubling down on a new GM truck. A Yukon Denali XL is 85K!! I dont care if something is 5K or 8K to change a Timing chain. He said its about 40 hours at 175 an hour thats still 7K. Much cheaper than getting killed on a trade and paying 85K to start a new story. I used to need a small reason to get a new truck every few years....But GM changed that. They make crap now and charge more for it. Its not fun anymore, its offensive. I can buy anything i want, but i won't. 85K for a GM truck...its crazy. A Mercedes GLS is 97K and very luxurious and high quality. Yes they have issues as all trucks do. At 100K I'll be out of warranty and fix what breaks.

Thoughts on purchasing a higher-mileage Duramax?

carguy79

TYF Newbie

Stbentoak

Full Access Member

blackelky

Full Access Member

ReaperHWK

Full Access Member

Marky Dissod

Full Access Member

Big Bad Allis

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dbphillips

Full Access Member

TiGrayMSM

TYF Newbie

petethepug

Michael

Seamus

Full Access Member

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