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.
IRON:
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.
COPPER:
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.
ALUMINUM:
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.
SOOT:
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%.
FILTRATION:
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.
