TBN/TAN CrossOver in UOA-- What Does It Tell Us?

[AMRoberts]

Originally Posted By: Gary Allan

What he meant was that it "shouldn't appear" linear when plotted on a graph if any of the multitude of UOA results are any indication of how it behaves in use.


I suppose the chart on page 16 of the presentation could just be an example of poor PowerPoint communication, but if so it is a lot worse than I'd expect from a collection of engineers.

The Lubrizol chart begins a zero (0) miles of oil use. Their TBN doesn't illustrate either the starting non-linear roll-off or then ending non-linear behavior seen in this Machinery Lubrication article (authored by Polaris Labs), which claims to graph fleet test results.

TAN on the Lubrizol chart seems even more at odds with the Machinery Lubrication article, not showing a nearly-constant TAN level early in the OCI.

 

[Gary Allan]

This would be more what I'd expect with the "Z" pattern to TBN.

I am curious on how that little "void wedge" formed just above the 65% depletion line.

Looking it over a bit more, it looks like the distribution of TAN is +/- along the TBN decay line and widens from there.

 

[The Critic]

Where did you get this chart from?

 

[Gary Allan]

GA: I'm not telling.
The Critic: What do you mean you're not telling?
GA: I mean I'm not telling! Privileged content. I'm not sharing.

http://www.machinerylubrication.com/Read/2170/oil-drain-interval-tan-tbn

 

[buster]

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2597028

Quote:
SUMMARY - It can be concluded that a judgment of
the quality of a lubricant, and especially it’s capabilities
for use as an extended service interval oil, cannot be
based solely on the TBN measurements. Several other
used oil characteristics need to be taken into account to
come to the correct conclusions. In the next sections,
the results of some bench test work,, triggered by ourthe
field test observations, will be discussed.

This paper offers some observations from a field
test, showing that some detergent approaches gave
unacceptable performance even though the TBNs were
at an acceptable level. It is hypothesized that some
detergents do not effectively neutralize all acidic species
present in the lubricant, and thereby thus reservinge
their own base, which shows up as TBN, while in fact
the oil may no longernot provide sufficient any protection
against bearing corrosion.


Quote:
Although the TBN
measurementss are informative, easy, and quick, it can
be misleading to base the judgment of an oil’s
performance solely on onethis one criteriona.