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TBN #5234518 10/09/19 06:39 AM
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borgward Offline OP
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What is the significance of the TBN number in an oil report? is higher or lower better?

Re: TBN [Re: borgward] #5234542 10/09/19 07:09 AM
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Char Baby Offline
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Higher is better to a point. This is where the pH starts out in a motor oil.
Base is the opposite of Acid. Base raises pH and Acid lowers pH.
For example, pH of 7 is neutral as in water(H2o). So it the case of motor oil, the more acidic the oil becomes, the lower the pH becomes. I guess that around a pH of <2, the oil is becoming too acidic for aluminum.

EDIT:
Not sure that I said all of that correctly. But from my lab experience, I know what I am trying to say.

Last edited by Char Baby; 10/09/19 07:11 AM.

Retired 6 yrs now & lovin' it
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'80 Firebird FORMULA V8/4bbl-purchased "NEW"
'15 Nissan Altima 2.5 SV
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Re: TBN [Re: borgward] #5234547 10/09/19 07:13 AM
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ZZman Offline
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Higher is better as it allows the oil to resist acid build up longer. Higher isn't really that important if you don't do long oil change intervals.


2005 Toyota Avalon XLS 3.5 motor
2014 Ford Fusion 2.5 motor
Re: TBN [Re: borgward] #5234552 10/09/19 07:19 AM
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FordCapriDriver Offline
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Some say that when the TBN drops below 3 it's time to change.


1975 Ford Capri II Ghia 3000 V6 - 315k, Repsol Elite Super 20W-50
1988 Ford Escort XR3i Cabrio - 110k, Valvoline Maxlife 10W-40

Re: TBN [Re: FordCapriDriver] #5234557 10/09/19 07:22 AM
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Char Baby Offline
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Originally Posted by FordCapriDriver
Some say that when the TBN drops below 3 it's time to change.




220/221.... wink


Retired 6 yrs now & lovin' it
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'80 Firebird FORMULA V8/4bbl-purchased "NEW"
'15 Nissan Altima 2.5 SV
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Re: TBN [Re: FordCapriDriver] #5234618 10/09/19 08:20 AM
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Donald Offline
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Originally Posted by FordCapriDriver
Some say that when the TBN drops below 3 it's time to change.



I would say between 1 and 2 you should change.

Its not linear also.


2015 Ford F-250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: TBN [Re: borgward] #5234639 10/09/19 08:37 AM
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borgward Offline OP
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The TBN,s were from 2.7 to 3.4. 2.7 was on 6551 oci and 3.4 was on 8988 oci. That 8988 was after taking a long road trip. wonder what TBI of new Mobil1 would be?

Re: TBN [Re: borgward] #5234641 10/09/19 08:38 AM
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FordCapriDriver Offline
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I personally always go for +10 TBN because i only really do around 6000 miles a year, and i have two cars so that's roughly 3000 each and i usually change at 4500 which comes out to 18 months.


1975 Ford Capri II Ghia 3000 V6 - 315k, Repsol Elite Super 20W-50
1988 Ford Escort XR3i Cabrio - 110k, Valvoline Maxlife 10W-40

Re: TBN [Re: borgward] #5234646 10/09/19 08:41 AM
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Quattro Pete Offline
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Originally Posted by borgward
wonder what TBI of new Mobil1 would be?
Which Mobil1? Look at the VOAs we have on this site. They'll usually show you that info.


2002 530i   2015 Q5 3.0T   2018 Charger SRT
Re: TBN [Re: Char Baby] #5234689 10/09/19 09:20 AM
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weasley Offline
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Originally Posted by Char Baby
Higher is better to a point. This is where the pH starts out in a motor oil.
Base is the opposite of Acid. Base raises pH and Acid lowers pH.
For example, pH of 7 is neutral as in water(H2o). So it the case of motor oil, the more acidic the oil becomes, the lower the pH becomes. I guess that around a pH of <2, the oil is becoming too acidic for aluminum.

EDIT:
Not sure that I said all of that correctly. But from my lab experience, I know what I am trying to say.

Sort of in the right place, but not technically correct.

pH is a measure of acidity and alkalinity in an aqueous medium ("pH" literally means "-log10[H+]", or minus log base ten of the concentration of hydrogen ions).

Oil is not an aqueous medium so the concept of 'acid' and 'alkali' is somewhat different and can not be measured or expressed as pH. TBN is a measure of an oil's alkaline reserve, which is used to neutralise acids. High or low is not good or bad because it depends on a number of factors as to what TBN is appropriate. Diesel engine oils tend to have higher TBN as diesel engines generate more acidic species in combustion. Longer drain oils have higher TBNs simply to allow them to carry on for longer. TBN drops in use, so the higher your starting point, the longer you go until the TBN is depleted.

High TBN in a UOA isn't always a good thing - the TBN is there to do a job - neutralise acids. If the TBN stays high then it isn't doing anything, meaning either there are no acids to mop up or that the acids are present but not being mopped up by the TBN. This idea of TBN retention is all very well, so long as the TBN is actually doing what its there for.


2017 SEAT Leon 1.4 EcoTSI 150 FR Technology DSG
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Re: TBN [Re: weasley] #5234754 10/09/19 10:17 AM
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Quattro Pete Offline
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Originally Posted by weasley
High TBN in a UOA isn't always a good thing - the TBN is there to do a job - neutralise acids. If the TBN stays high then it isn't doing anything, meaning either there are no acids to mop up or that the acids are present but not being mopped up by the TBN.
This is why it's helpful to know TAN as well.


2002 530i   2015 Q5 3.0T   2018 Charger SRT
Re: TBN [Re: borgward] #5234805 10/09/19 11:06 AM
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PiperOne Offline
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^^THIS!!^^ 100% spot on.


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Re: TBN [Re: borgward] #5234862 10/09/19 12:17 PM
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JLTD Offline
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Originally Posted by borgward
What is the significance of the TBN number in an oil report? is higher or lower better?


TBN = Total Base Number. As mentioned, it is the protective additives in the oil.

Too low is bad; I base my condemnation level on Blackstone's recommendation of no lower than 1.0, going conservative at 1.5. Most of my runs never reach that level.

On the UOA, compare the TBN with the starting TBN of the oil; but that is not all to look at to determine interval. Check also the viscosity to see if it has thickened or thinned out of grade. Also check for coolant, water, and insolubles, all of which tell more about your oil's condition.

I might suggest some reading of UOA threads, plenty of information there to assist in learning what you want to know.


Lates.
Re: TBN [Re: ZZman] #5234872 10/09/19 12:29 PM
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Mad_Hatter Offline
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Originally Posted by ZZman
Higher is better as it allows the oil to resist acid build up longer. Higher isn't really that important if you don't do long oil change intervals.

True having a high(er) TBN is desirable when doing long oci's but even on short oci's a high(er) TBN can be desirable. If you have excessive blow by or dilution, these can accelerate oxidation and the formation of harmful acids.

Re: TBN [Re: weasley] #5234878 10/09/19 12:35 PM
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Mad_Hatter Offline
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Originally Posted by weasley

High TBN in a UOA isn't always a good thing - the TBN is there to do a job - neutralise acids. If the TBN stays high then it isn't doing anything, meaning either there are no acids to mop up or that the acids are present but not being mopped up by the TBN. This idea of TBN retention is all very well, so long as the TBN is actually doing what its there for.

Indeed reserve alkalinity is important and I've personally NEVER seen a UOA where the oils reserve alkalinity didn't drop by some amount. Every engine experiences blow by on some level... it's what's in the blow by that creates acids in the crankcase. I don't see how an oils reserve alkalinity could be unaffected by this most basic of engine processes. But maybe I'm missing something..🤔

Last edited by Mad_Hatter; 10/09/19 12:35 PM.
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