Dodge Durango 3.6L - HPL CK-4 5w-20 - 33,300 miles on oil - 173,000 miles total

[wwillson]

Did you break you arm doing cartwheels and such over the impressive results because I would have

Nope, I was stoic and showed zero emotions.

 

[dnewton3]

The Fe wear rate in the last 5k miles is around 3 times higher than in the first 28k miles. Aluminum is up significantly as well. I'd interpret this as a condemnation point, especially since Fe/mile usually trends down over an OCI (which probably has more to do with the iron getting filtered out or ending up in deposits than the actual wear rate). So actual wear may have been more than 3x higher.

The last long run also saw more than a doubling of the Fe wear rate in the final 5k. In both cases, the increased wear rate was just after the oxidation measurement hit 24.

Now, a low wear rate that increases by a factor of 3 is still a low wear rate, but if all the additional wear is from a single component that really doesn't like the aged oil, it could be that the wear on that component is much higher than normal.

If this were my vehicle, I'd consider oxidation at 24 to be a condemnation limit. I'd maybe do a UOA at 22k, then decide from there how much longer the oil should go, but in the interest of science, I think you should do another 5k

I disagree with your assessment, in part.

I do agree with you comments regarding the potential for singular vs. multi-element component wear. UOAs cannot tell us if one cam lob is wearing, or several cylinder walls are wearing. UOAs cannot locate wear with that manner of accuracy. But, that's not unique to this series of UOAs; that's true of all of them. We also must admit that singular events can cause UOA data spikes; particle streaks in particular are phenomenons which cause consternation in UOA data analysis. A particle gouges into metal, and then that event sloughs off for a while; sort of like a slow coagulation of blood after a cut.

When the UOAs are of the same sump load, UOA wear rates are run in a cumulative manner, not individual events; that's the industry practice.

The last 5 UOAs:

Fe wear rates (ppm/1k mi)
1.3; 1.3; 0.9; 0.8; 1.0
Now, only 5 samples exist in this set; nowhere near enough to understand standard deviation. Further, we don't know about the gauge R&R of the analysis process. But what we do know is that these rates are low enough that they are only moving by thenths of a ppm. If you understand statistical quality control, then we have to admit that it's improper to report results at a magnitude lower than what the base data comes in at ... But we do what we do here to get a sense of the issue. The reality is that splitting hairs so fine has inherent issues in reporting. Unfortunately, that's all we've got.

Al is definitely going up. But not at an alarming rate, nor anywhere near a condemnation point.


There are no published condemnation wear data for the Pentastar 3.6L engine that I'm aware of. (Pretty much any light-duty gas or diesel engine maker doesn't publish these values, and I doubt they have any data that would even internally give them an idea). OTOH, makers of large diesel engines (like Cummins, Volvo, DD, etc) all have had statements published in some form or another; they do give values for condemnation levels. Typically, for Fe as an example, you'd see (depending on brand of engine) anywhere from 100ppm to 150ppm. That's a content max limit; not a wear rate. So the reality is that we don't know what content limits would be prudent here, but 33ppm of Fe certainly isn't enough to be a slurry of death by any stretch of the imagination. As for Al, most of the OEs in the heavy engine market use anywhere from 35 to 50ppm. Is that germane to this engine? Probably not. But we have nothing else to use, either.

Oil condemnation has be understood from not one, but several points of view.
- wear rates
- total wear content
- physical properties
- contamination content
- etc
Any one known value is only a part of the overall picture. In this series of UOAs, we see nothing in terms of the lube that is so concerning that an OCI is warranted. As far as wear goes, there was nothing wrong with this sump load.


The concern for wwillson ultimately became the insolubles; the oxidation was causing filter loading past a comfortable limit for him. The fear being that as the oxidation crept up with the OCI maturity, the filter loading rate might have eventually caused a permanent bypass event; something he's unwilling to experience. The metal wear rates were perfectly acceptable, and no reasonable content limit had been reached; had it not been for oxidation, the OCI would still be ongoing.

My point is that just because wear is going up, does not mean that wear rate increase is automatically detrimental. It needs to be understood in context, looking at the totality of the circumstances and not in a vacuum.


I would, if I were him, run the next OCI out to 30k miles, and see if the results from this current UOA series can be replicated reasonably close in the next series.