Importance of keeping TBN High

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Just read this: http://machinerylubrication.com/Read/2170/oil-drain-interval-tan-tbn .

The graphic shows a study of 450 delivery trucks, and found that at some point before TBN falls to half of the original value, TAN starts to rise; and when the TBN hits the 1/3 (of the original amount) point, it starts to fall rapidly.

I don't seem to see much of a reaction (here by posters at BITOG, or by Blackstone itself) when Blackstone sends the UOA, and they simply want to see the TBN at at least 1.0. I realize there are different ways to determine the TBN, but I'm still thinking that either way, 1.0 is going to be pretty darn low.

So is concern about changing oil when TBN drops, a fools errand--or a solution looking for a problem? I mean, what is happening in the engine in the cars toward the right side of that graphic--and is it anything anyone needs to be concerned about? Does a TAN that is higher than the TBN mean that metal parts are literally getting eaten up? Or simply that if the oil isn't changed in another month or two, you might see this?
 
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Its just a single data point.

Oil failure has multiple points.

But, I don't see pushing any single point to the brink to prove anything.

The real question to ask, is Blackstone 1.0 TBN an issue? or does it have a built in cushion that Blackstone understands based on the gazillions of UOA data that they have? and compared to other lab's TBN method?

TBN/TAN... good to see if you extend oil intervals to prevent running the oil beyond a safe TBN level, or TAN point. But, probably not needed by many that maintain based on time/mileage/experience.
 
Originally Posted By: Greasymechtech
Its just a single data point.

Oil failure has multiple points.

But, I don't see pushing any single point to the brink to prove anything.

The real question to ask, is Blackstone 1.0 TBN an issue? or does it have a built in cushion that Blackstone understands based on the gazillions of UOA data that they have? and compared to other lab's TBN method?

TBN/TAN... good to see if you extend oil intervals to prevent running the oil beyond a safe TBN level, or TAN point. But, probably not needed by many that maintain based on time/mileage/experience.



Some interesting points there. If we're talking about a 5 or 6K mile OCI, I suppose TBN would be nothing to worry about. But even then, maintaining a high TBN would be one reason for keeping the OCI that short to begin with.
 
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No buffered solutions have a linear titration (depletion) curve.

They go very slowly until most of the buffer has been consumed / neutralized, then drop sharply.

What you don't want to do is run out of (in this case) base. You want to dump before you go beyond the equivalence point, so in this case you dump before you reach the equivalence point, while the solution is still alkaline.

How close is too close? That's an individual judgement.

PQIA suggests dump if TBN < 3.

http://www.pqiamerica.com/TBN.htm

A set of UOA data certainly can be used to get closer.
 
OK, so two expert opinions would say change oil when it is less than 3, or less than 1.
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What would happen if the TBN falls to less than 1.0? Apart from Blackstone telling you to cut your next OCI short by 1000 miles.
 
Originally Posted By: Greasymechtech
Oil failure has multiple points.

Exactly. We have had some very expert commentary here on UOAs where TBN wasn't even tested. We shouldn't get hung up on merely one data point.
 
an amsoil site had a paragraph on acid corrosion: http://www.syntheticoildistributor.com/Factors-For-Motor-Oil-Failure.html

Some interesting info (in that paragraph under the title, "Too Acidic").

OK, so it seems like what would get corroded would be parts of the engine that the oil touched. This leads to another question:

If some highly acidic oil gets on engine parts, and then there is an oil change, would the new oil with a much higher TBN then be able to neutralize the acidic wear on the parts? Or would it be too late then? If so, that might alleviate some of the concern about changing oil if the TBN got below 3.
 
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I sent an oil sample to Blackstone with 8,000 miles on it. The wear numbers were excellent but the TBN was 1.0. Blackstone suggested I go an additional 1,000 miles.
 
OP you are over thinking this. Metal parts being "eaten up" is an exaggeration just because TBN is in the 1-2 range. I do 10K OCIs(have since 1978) and I don't do UOAs at all. I have no interest in them.
 
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I agree. If you are really concerned to that degree, forget the UOA and take the money and do another oil change at super safe intervals. I say this this only to alleviate worries and not to be smart.



Originally Posted By: tig1
OP you are over thinking this. Metal parts being "eaten up" is an exaggeration just because TBN is in the 1-2 range. I do 10K OCIs(have since 1978) and I don't do UOAs at all. I have no interest in them.
 
Originally Posted By: AirgunSavant

I agree. If you are really concerned to that degree, forget the UOA and take the money and do another oil change at super safe intervals. I say this this only to alleviate worries and not to be smart.


Fair enough. I raised the question because an oil change at 6K is something I have been thinking about, although of course if I am going to set up a routine of shorter OCIs, I'd like there to be some reason. If I need to change the oil when the TBN reaches 1.0, I can plan for a much longer OCI than if I need to change it when it falls to one third of the original level.
 
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Thanks for the Machinery Lubrication link in the initial post. They mention points when TBN reaches 5.5-6, and TBN/TAN crossover around 3.5. Not sure why one would consider waiting until TBN drops to 1.
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Anyway, this allows me to better interpret the TBN shown on my Wix UOA reports.
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Originally Posted By: paulri
Originally Posted By: AirgunSavant

I agree. If you are really concerned to that degree, forget the UOA and take the money and do another oil change at super safe intervals. I say this this only to alleviate worries and not to be smart.


Fair enough. I raised the question because an oil change at 6K is something I have been thinking about, although of course if I am going to set up a routine of shorter OCIs, I'd like there to be some reason. If I need to change the oil when the TBN reaches 1.0, I can plan for a much longer OCI than if I need to change it when it falls to one third of the original level.


Not necessarily. If you choose an oil with a fresh oil TBN of 3, both criteria are satisfied simultaneously.

Hopefully this helps put perspective on the two methodologies suggested?

Personally, when I look at the graph in the article you posted a link to, there are so many pale blue squares showing such scatter in the data that any time TBN is < 6 or so on that graph is where a significant number of pale blue squares appear above the red horizontal line in the graph.
 
If you really want to extend your oci, then as the article says:

Quote:
Monitoring TBN, Viscosity, Oxidation and Nitration simultaneously and changing both the oil and filters when contamination from dirt, coolant, fuel dilution or soot reaches critical alarm limits is ultimately the best way to determine optimal engine oil drain intervals regardless of the time on the oil.
 
Originally Posted By: Nyogtha
paulri said:
Not necessarily. If you choose an oil with a fresh oil TBN of 3, both criteria are satisfied simultaneously.

Hopefully this helps put perspective on the two methodologies suggested?

Personally, when I look at the graph in the article you posted a link to, there are so many pale blue squares showing such scatter in the data that any time TBN is < 6 or so on that graph is where a significant number of pale blue squares appear above the red horizontal line in the graph.


I haven't yet seen a fresh oil with a TBN of 3. I have 3 VOAs (M1, M1EP, and PY) and the lowest is M1 with 6.7. The others are 9 & 8.8.

But yes, your attention to the different methodologies raises a fair question. Going back to that graph, it is the absolute numbers or the fraction of original strength, that we need to look at? Is it when TBN reaches 1/2 & 1/3 of original strength that we need to be concerned, or when it reaches 6 & 3?
 
Another angle on TBN is proposed in this study. This study (which has a graph of the TBN and TAN) says that when the two intersect, that TAN then rapidly rises, and that this increased acidity will cause corrosion (although it doesn't say how soon it will be, or how much corrosion). But this intersection of TBN and TAN is given as the ideal point for an oil change.

Looking at Figure 1 (page 4), it appears that these intersection points are rather similar to the one third mark (for 3 of the 4 oils charted).

One caveat against drawing too many conclusions from this one study, is that it was focused on Turkey, where there was a lot of sulphur in the fuel. I'm not sure when the study was presented; it appears that it was done in the year 2000.
 
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That graph has some features I've never understood.

What's the X-axis, and how do they get away with publishing a graph without it labelled (assuming they have editors who know their arse from their elbow)?

I'd guess OCI (time) would make sense. A plot of TBN against TAN would too.

Why that clear "wedge" under the TBN line, the bit with no TAN points? (The TBN line is perhaps "theoretical". There's no way that's real raw data, though I suppose it COULD be a fitted curve).
 
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Originally Posted By: paulri
Originally Posted By: Nyogtha
paulri said:
Not necessarily. If you choose an oil with a fresh oil TBN of 3, both criteria are satisfied simultaneously.

Hopefully this helps put perspective on the two methodologies suggested?

Personally, when I look at the graph in the article you posted a link to, there are so many pale blue squares showing such scatter in the data that any time TBN is < 6 or so on that graph is where a significant number of pale blue squares appear above the red horizontal line in the graph.


I haven't yet seen a fresh oil with a TBN of 3. I have 3 VOAs (M1, M1EP, and PY) and the lowest is M1 with 6.7. The others are 9 & 8.8.

But yes, your attention to the different methodologies raises a fair question. Going back to that graph, it is the absolute numbers or the fraction of original strength, that we need to look at? Is it when TBN reaches 1/2 & 1/3 of original strength that we need to be concerned, or when it reaches 6 & 3?


Here's one with a fresh TBN < 2.

http://www.pqiamerica.com/June 2014/xpress5302015.htm

There are a LOT of oils with fresh TBN < 5 on the PQIA site. Personally, I wouldn't purchase any of those oils.

Originally Posted By: Ducked
That graph has some features I've never understood.

What's the X-axis, and how do they get away with publishing a graph without it labelled (assuming they have editors who know their arse from their elbow)?

I'd guess OCI (time) would make sense. A plot of TBN against TAN would too.

Why that clear "wedge" under the TBN line, the bit with no TAN points? (The TBN line is perhaps "theoretical". There's no way that's real raw data, though I suppose it COULD be a fitted curve).


I would say time is correct for the X-axis.

This is simply the charachteristic neutralization / titration curve for a buffered solution. A short steep section, a much longer lower slope section, then a short steep section. As you pass the equivalence point, the buffering works for the other species as well (in this case acid). The short, near-vertical sections portray the danger in trying to linearly predict depletion.

Personally, it looks to me like PQIA is on track with their recommendation to change when TBN < 3. That's right about where the curve transitions back to near vertical with poor predictability on how much further it can go before TBN runs out.
 
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