2021 Chevy Duramax L5P - 13,500 miles on oil/16,000 total vehicle miles - HPL 5w-40


Staff member
Aug 20, 2003
Naperville, IL
This is a 2021 Chevy 3500 DRW L5P Duramax that pulls a 20,000 pound 5th wheel for a combined GVW of 29,000 pounds. We pull at 65 MPH, which is 1,400 RPMs in 10th gear. The engine is capable of about 200 HP at 1,400 RPMs and averages 9.5 MPG while towing and about 20 MPG not towing. Developing 200 HP at 1,400 RPM almost continuously requires pretty high boost and really heats everything up, including the oil. I added 1.5 quarts of makeup oil, which included the oil for a filter change. The wear metals are at a reasonable level and would probably be better if the engine didn't work so hard. Potassium should be watched, but I found several other Duramax UOAs that had much higher levels of potassium and didn't seem to have any problem. Glycol was Negative, which does ease my mind a bit about antifreeze intrusion. The make-up oil probably explains the increase in TBN and the decrease in Si and Al. I will resample in July and should have about 18,000 miles on the oil.

Lab is Wearcheck

Sample Information
Sample Date6/23/202107/17/20218/24/20214/4/2022
Machine Age miles2,5002,7008,90016,000
Oil Age miles2,5002006,40013,500
Machine Time hours5562214350
Oil Time hours557152295
Filter Age miles2,5002006,4007,100
Oil ChangedYesNoNoNo
Filter ChangedYesNoYesYes
Make-up oil0001.5 qts
Viscosity15-405w-40 CK-45w-40 CK-45w-40 CK-4
Wear Metals
Fuel %<1<1.0<1.0<1.0
Fluid Condition
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Are you still using the fuel additive to help reduce Regens? I know that was a contributor to Fe as well, right?

GM does not publish condemnation limits for wear metals. Many other manufacturers like Cummins, DD, etc place a limit at 100ppm for Fe. What's your planned limit?
I think the iron is to be expected seeing that there have not been many oil changes and it was probably still breaking in through 10k miles.

Soot is only .6 at 13k miles. Does not seem bad at all.

That oil looks pretty stout with a tbn over 13 at 13,500 miles.
I was going to ask you that, since you are the resident Duramax expert. :)

Dave @High Performance Lubricants may have some insight on FE condemnation limits.
There's a couple things to watch for regarding condemnation limits; wear rates and wear totals. Either one needs to be considered as a separate issue.

Right now, your wear rate for Fe is staying fairly constant; about 5.6ppm/1k miles and 5.0ppm/1k miles for these last two UOAs. The wear rate itself is higher than statistical norms, but given the hard use it may be considered acceptable. When the Fe wear rate starts to rise, I'd say the OCI is warranted, given the already high magnitude.

The wear total limit for Fe is a different topic. As I said, many other OEMs consider between 100ppm to 150ppm to be the upper end limit for oil Fe saturation. For light duty trucks, companies don't publish limits for the PSD's, the Dmax's and the ISB's (though Cummins does publish limits for their larger engines at 100ppm as I recall). The theory is that enough material is floating around that it can become counter productive to retain the lube because of the abrasive nature of the Fe. I would say the condemnation limit for Fe should be towards the lower end of that range, because light duty diesels are not "built as heavy" as larger OTR and OR diesel engines which have the intent of easy rebuilds (sleeved bores, etc). So maybe consider 100ppm as your target? ... given the steady wear rate, you can predict that the potential OCI should be around 20k miles or so given this current load, assuming no drastic change in wear occurs.

I presume the Cu level is from the oil cooler reaction to amines, or whatever else HPL may have in the lube. It would be too hard to tell if the Cu is coming from elsewhere; the levels are far too high to be called "normal". It'd be nearly impossible to tell you what wear total is a limit here, because it's impossible to tell "wear" Cu from "reaction" Cu here. Cu being a soft metal isn't going to really be detrimental as a wear contributor; it's just a wear indicator.

The Al level isn't that bad, which is good. The normal wear rate is around .5ppm/1k miles, and your's is nearly double that, but given the hard pulling, that's to be expected. You're around 1ppm/1k miles, so as long as it doesn't escalate quickly, that wear rate would be fine IMO. If the wear rate spikes, it's time for an OCI. As far as a total limit, I don't know that Al is as critical, as it's not nearly as hard on other metals, so it's probably not something to concern yourself with. The wear rate is the thing to watch here; if it spikes, something is wrong and needs changed ASAP. Al isn't as hard as Fe, but it's harder than Cu, so keep that in mind. Other than Cummins, you won't find an OEM limit of Al, but many labs do place a limit on Al; typically around 30-40ppm. Cummins limit is 15ppm, but again, that's based on their heavier engines and not the ISB as far as I know. So if you accept the 15ppm limit, you're already pretty much there. If you accept the 30-40ppm limit, you still have some headroom. It's your call here.

Generally accepted between 3% to 5% depending on OEM as a limit total. You're well below that so all's good there. I'm not sure what wizzardry chemicals HPL uses to control soot amalgamation. The TBN can be of assistance here as well; and it's heavily dosed up for sure. So I'd not worry about soot until it would reach 3% or more. 3% would be my "starting watching closer" number. If the soot gets to 3%, and all the wear metals look safe, it's say it'd be OK to go further. But if soot is 3% and the wear metals are higher, I'd not push it much past 3%.

You're in a position to perhaps consider BP filtration. That may well help lower the Fe load. The concern here is that UOAs are only picking up a portion of the metal loads. There's certainly much larger Fe particles in suspension going around and around with each gallon circulated than what we're seeing. When the UOA indicates low wear values, the larger particle load isn't a big concern. But when the UOA data shows high Fe counts, you have to concern yourself with the larger particle loading. This is exactly where a BP filter can make a very important difference. Extend OCIs by their nature make for high particulate loading, and reducing that load is paramount to continuing the OCI. Given the very strong additive package in the HPL, I'd think that BP filtration could make for some really long OCIs. BP filtration will bring all the wear metals down in concentration. If you don't choose to use BP filtration, you're going to reach the condemnation limits very soon most likely. BP filters are non-discriminatory; they'll catch anything 3um or larger, which is very beneficial. Doesn't matter if it's soot or Fe, the BP will catch it. Something to consider if much longer OCIs are your goal.
*Note.... I'm a big fan of BP filtration when it makes sense. BP filtration does not make sense in all situations. Normal OCI durations will never see any major benefit from BP, simply because the loading isn't high enough to warrant the expense; I do NOT advocate the use of BP filters for "normal" OCIs. But greatly extended OCIs are the primary condition for BP application; makes very good sense and can have a major impact on controlling wear and soot. It becomes a game of ROI maximization; at what point does the BP filter system break even on costs, relative to the cost of an OCI? A detailed analysis is the only way to know.
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Great analysis Dave, thank you.

My plan is to change the oil after the next sample, as we should be near the 100ppm Fe, which I think is a reasonable value. Since much of the break-in wear is still in the oil, I would expect the wear metals to get better in subsequent samples with fresh oil.

I have considered bypass filtration, but other than a fun experiment, I don't see the ROI. However, you know me, the perpetual experimenter, I could possibly be convinced.
Great analysis Dave, thank you.

My plan is to change the oil after the next sample, as we should be near the 100ppm Fe, which I think is a reasonable value. Since much of the break-in wear is still in the oil, I would expect the wear metals to get better in subsequent samples with fresh oil.

I have considered bypass filtration, but other than a fun experiment, I don't see the ROI. However, you know me, the perpetual experimenter, I could possibly be convinced.
Is this the STD version of the 5w40 or the cold climate version?
We have a 2021 durax in the fleet with 170k miles now. Nothing but issues from injector connectors, def tank, exhaust manifold leaks. Keep on top of it we run delvac 15w40 with 10 to 15k mile changes now. Motor is running strong everything else around it sucks