2018 Chevy Duramax L5P - 5,500 miles 25,000 miles total

wwillson

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Naperville, IL
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As you may have read, I was a bit concerned about the last analysys on my Duramax in this thread: https://www.bobistheoilguy.com/foru...000-miles-19-500-miles-total#Post5255959 I just got this sample back today. Nothing to see folks, move along :-) Even with the Fe based fuel additive, the Fe number is good. We also found that the oxidation number of virgin Delvac 1 ESP is 33, so nothing to worry about there either.

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dnewton3

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Indianapolis, IN
Cu is typical of newer Dmax engines, and given the use a PAO; again not unexpected for a longer period of chelation to occur before settling down. The unit and lube times are shown as "mi", but actually are hours in his data. 5500 miles / 120 hours is around 45 mph as an average; very typical. Congratulations Mr. Willson - you've got yourself one boring engine there! thumbsup But then again, it's a Dmax. We'd expect nothing less. No matter the lube or the miles, that's pretty much what all of them do. I've gotten to the point where I often advise folks to just forego the UOAs in a Dmax, if they intend to follow the IOLM or less. There's never anything to see of any value; you don't learn anything other than how completely "normal" these engines are. What few examples I've seen of Dmax UOAs out of control are attributed to severe abuse (tuning up to 1000 hp, etc) and/or stupid maintenance practices (running 15w-40 with a Lucas vis thickener, and then using an oil filter that has no BP in it .... yes - that actually happened). Other than those extremes, the Dmax is like the Honey Badger - it just don't care.
 
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dnewton3

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Indianapolis, IN
25%, eh? Clearly an ultra-conservative figure given the status of the wear and condition of lube. But it's been my experience that typically IOLMs are just that; expressions of conservative OCIs still aimed at limiting the OEMs warranty risks. IOLMs are better than pure mile-based hard limits; at least IOLMs take into account things like ambient temps, engine temps, loading factors, idle times, etc. Think of OCIs in this typical manner: good, better, best - Good is doing your OCIs based on some arcane arbitrary limit written in a manual; every 3k miles, 5k miles, etc. There's no accounting for actual state of engine or lube; these are just safe guesses based on decades old mantra. - Better is using the IOLM. At least operational conditions and environmental parameters are taken into account. These are run in an algorithm and spit out a % oi life. But that delineation is still driven by overly conservative demarcations. - Best is doing UOAs. These give us indications of both the lube condition and engine wear. These are not guesses based on inputs; these are results based on outputs. 10k miles in this case is a no-brainer. Probably can go past that will little concern, but I would advocate for structured and monitored increases and not a full-on blast out to some wild assumption.
 
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