There’s no date stamp anywhere in that article. Any idea how old it is?
Well it's discussing the change from CI-4+ to CJ-4, so about 13 years old give or take a year!
I'm on record as to saying that TBN/TAN is often very misunderstood. And I'll keep beating that drum until some folks actually listen.
TBN/TAN is important, but only as an input and not an output. Wear metals tell the real story about how things are going. Most all other things are inputs (Vis, FP, base/acid, etc).
Inputs are predictors, they are NOT results. There are thousands upon thousands of UOAs where the TBN has been low, and/or there's been an base/acid cross-over, and yet wear metals go unaffected. Back when diesel fuel was loaded with sulfur, and the crankcases were "open" (PCV vented to atmosphere), then acid build up was a big concern in longer OCIs. Back then, seeing a cross-over was a tell-tale sign that wear was about to uptick. But today, with ULSD and closed vent systems, this isn't as big of a deal. And more importantly, it's still just a predictor of things that MIGHT change at some point in the FUTURE. The inversion of base/acid is not, in and of itself, an assurance that wear is suddenly going to just skyrocket. There is ZERO proof of this being true. There is not one case of the base/acid inversion immediately resulting in wear rate escalation in over 15,000 UOAs I've processed in my database. If there were a trend, I'd know it for sure. Folks - it ain't there.
UOAs are tools, they are not 100% assurances of perfection, nor is any tool perfect. They have to be understood in how/when to use them. The base/acid topic is just a tool within a tool. You have to know what it represents and how to use the info. Seeing low TBN or a cross-over of base/acid does NOT IN ANY MANNER MEAN THAT THE OIL IS BAD OR THE ENGINE IS IN DANGER. What it means it that when that threshold is crossed, it's time to pay closer attention to the wear metals.
If you are doing extended OCIs, and you're doing your UOAs every 10k miles, and then you see a TBN/TAN cross-over happen, it's time to start maybe taking your UOAs at 7.5k miles; a bit sooner and more frequently to track the POTENTIAL shift in metals, indicating a uptick in a wear trend. And just because that uptick happens, it's not time to panic. If you're doing extended OCIs with UOAs, you should be managing the sump to reasonable condemnation limits for totals and rates.
But just like we see preset limits on OCIs from the OEM (often ultra conservative as a means of over-protection), the topic of base/acid is similar. There's no proof that the inversion of the base/acid realtionship will result in immediate wear escalation; but it's easy for the pundits to simply use that as a trigger for an OCI, as an over-reaction of safety measure. It's easier to just put a simple black-and-white rule on a piece of paper than to explain the real reason to use the tool, and then teach folks how to properly use it. There's no proof that a 5k mile OCI is truly the best decision in terms of wear and costs, but it's easy to print in an Owner's Manual. And there's no proof that doing an oil change is safer or cost effective when the TBN/TAN inverts, but it's easy to print in a manual or post on a website, and then have the gullible follow along because they are uninformed and don't know what it really represents or why to use it.
INPUTS are things to track as potential indicators of future wear trend shifts. Vis, FP, TBN/TAN, etc all are physical characteristics of the lubes that, when in spec, indicate all it well. But when they go out of spec, it's not an assurance that wear is going to just blow-up; it's only an indication that it's time to start paying closer attention to the outputs. It's a tell-tale sign that things MIGHT shift sooner than you had previously expected, and so you need to pay closer attention a bit more often. THAT is how/why to use inputs. They are not, in and of themselves, a reason to change oil or panic. Only if a characteristic QUICKLY went WAY out of spec (a 20 grade becomes a 50 grade due to sever over-oxidation and thickening additives, for example) would it be prudent to do an immediate OCI, as an example.
Most of you whom know me, realize that I'm a data-driven person. Over 15k UOAs in my database, and adding every day. I can see trends (or the absence of them) far sooner than most pundits. It's not that TBN/TAN are not important in extended OCIs; they most certainly are. But they are not a cause for OCI panic. They are a tool within a tool; they are an input to an equation that has an output. Pay attention to the outputs; use them as your guide for OCIs. The inputs are predictors of potential change, and nothing more.
Hope that clears up the topic for some of you.