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#3250603 - 01/16/14 07:23 PM TBN, TAN, Ca, Mg, base-oil quality, oil life
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
I revisited this old Chevron Oronite reference about TBN retention and Ca vs. Mg detergents.

It studies oil life and wear in diesel engines. TBN measures the amount of acid-neutralizing detergents (Ca- or Mg-based) in the oil and TAN measures the amount of acid in the oil. Here is what I gathered from the paper, even though this is subject to ongoing research and debate:

(1) Neither TBN nor TAN alone can tell you the condition of the oil.

(2) TBN retention -- how slowly TBN decreases during service -- has no importance.

(3) Oil life or the ability of an oil to provide protection is determined by the difference of TBN from TAN = TBN - TAN. If TBN - TAN becomes negative, oil can no longer protect against wear and corrosion, the problem becoming worse and worse with a more negative number. The more positive TBN - TAN, the better the wear protection is.

(4) Initial TBN (fresh-oil TBN) is very important. Higher the initial TBN, the better it is. With a higher initial TBN, it will take the increasing TAN longer to reach the decreasing TBN.

(5) In general, Mg-based detergents are bad because they can't neutralize certain kinds of acids. Ca-based detergents are good in neutralizing virtually all kinds of acids. With Mg-based detergents, it could be misleading as TBN doesn't go down as rapidly but TAN increases more rapidly, as the Mg-based detergents aren't fully used in neutralizing the acids. Mg-based detergents also fight and oxidize the base oil.

(4) Acids are not only produced through combustion (NO_x and SO_x from the burning of the fuel) but also through the oxidization of the base oil. Therefore, higher the quality of the base oil, the better it is. PAO is better than Group III, and Group III is better than Group II for producing less acids in the oil.

(5) Wear metals increase with the acids, especially certain wear metals.

For me this is very interesting because I had thought that if TBN was above 2.0 or 3.0, it was fine. On the contrary, that's not the case at all. In fact, I worry even more now with the modern engine oils having smaller and smaller initial TBNs.

PS: Here is another good reference on oil life, also talking about other elements.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3250615 - 01/16/14 07:29 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
Rand Online   content


Registered: 08/20/03
Posts: 7773
Loc: Barberton,Ohio
you leave out key points such as detergents competing with antiwear additives etc.

Why you should leave this kind of stuff to the chemical engineers, and not use additives like willy wonka.

In other news I passed a giant lubrizol plant today in brecksville ohio.. no idea one was there.


Edited by Rand (01/16/14 07:30 PM)
_________________________
2015 Forester I-Premium 6MT


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#3250617 - 01/16/14 07:31 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
gregk24 Offline


Registered: 04/13/13
Posts: 2929
Loc: FL, USA
Interesting, but the truth is I probably change my oil before any of this becomes a concern.
_________________________
2006 Honda Accord LX 2.4 i-vtec 125K
Mobil 1 AFE 0w20
Fram Ultra 7317

2005 Chevy Uplander 3.5 117K
Mobil 1 HM 5w30
Fram Ultra 3387

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#3250651 - 01/16/14 08:11 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
Quattro Pete Offline


Registered: 10/30/02
Posts: 25921
Loc: Michigan
Originally Posted By: Gokhan
(3) Oil life or the ability of an oil to provide protection is determined by the difference of TBN from TAN = TBN - TAN. If TBN - TAN becomes negative, oil can no longer protect against wear and corrosion, the problem becoming worse and worse with a more negative number. The more positive TBN - TAN, the better the wear protection is.

While I generally agree, the article you linked to talks about the importance of these factors in diesel engine oil. Many believe that TAN is important in diesel engine applications, but less important in gasoline engine applications. Blackstone certainly believes this.

Also, that paper was written in 1997. Nowadays we have modern oil chemistries that have fairly high starting TAN. Does that mean they can't last as long as the oils made back in the 90s? I don't think so.

Quote:

With a higher initial TBN, it will take the increasing TAN longer to reach the decreasing TBN.

That assumes that the rate of TBN depletion as well as TAN uptake of various oils is the same. Yet we know very well this isn't always the case.

Quote:

For me this is very interesting because I had thought that if TBN was above 2.0 or 3.0, it was fine. On the contrary, that's not the case at all. In fact, I worry even more now with the modern engine oils having smaller and smaller initial TBNs.

PS: Here is another good reference on oil life, also talking about other elements.

Yup. This is why Wearcheck keeps condemning my UOAs, even though my TBN was above 4. They actually use a rule of thumb that if TAN reaches 80% of TBN, they suggest the oil be changed.
_________________________
'02 530i (PU 5W-40)
'08 C300 4Matic (M1 0W-40)
'13 F700 GS (BMW HP 15W-50)

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#3250724 - 01/16/14 09:54 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Quattro Pete]
Jeffs2006EvoIX Offline


Registered: 02/28/10
Posts: 1294
Loc: Imperial Valley, California
[/quote]
While I generally agree, the article you linked to talks about the importance of these factors in diesel engine oil. Many believe that TAN is important in diesel engine applications, but less important in gasoline engine applications. Blackstone certainly believes this[/quote]

This may be true my last UOA showed my TBN was 3.3 TAN was 5.1. According to this read M1 0w40 is killing my engine.

Though my car is gas not diesel so it must not apply? hornets

Jeff
_________________________
2013 VW GTI

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#3250758 - 01/16/14 10:46 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
Noobie Offline


Registered: 11/23/11
Posts: 127
Loc: None
Kind of a nice summary.
_________________________
03 BMW 525i M54 - / Everclear 10W-30
10 BMW 530i N52K - / MaxiGuard 10W-40
12 Audi A6 V6 2.8FSI - / Orbit 10W-40

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#3251105 - 01/17/14 11:25 AM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
btanchors Offline


Registered: 04/10/04
Posts: 570
Loc: Herndon, VA
I wonder if a better indication today would be UOA_TBN - (UOA_TAN - VOA_TAN). In other words, if the increase in TAN is greater than the current TBN, then you should condemn the oil at that point. This may be a better indicator given the high starting TAN of many oils today...Any comment?

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#3251147 - 01/17/14 12:03 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: btanchors]
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
Originally Posted By: btanchors
I wonder if a better indication today would be UOA_TBN - (UOA_TAN - VOA_TAN). In other words, if the increase in TAN is greater than the current TBN, then you should condemn the oil at that point. This may be a better indicator given the high starting TAN of many oils today...Any comment?

No, starting TANs are high today due to the ashless (nonmetal) succinimide dispersants that have been required thanks to SN/GF-5, which are acidic. SN/GF-5 has required more dispersants than in the past in order to better fight against sludge. However, on the down side, dispersants are acidic (corrosive) and they reduce the effectiveness of ZDDP, moly, and other antiwear and friction-modifier additives.

So, no, you need to look at the UOA TBN as well as UOA TAN.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3251161 - 01/17/14 12:19 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Quattro Pete]
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
Originally Posted By: Quattro Pete
Originally Posted By: Gokhan
(3) Oil life or the ability of an oil to provide protection is determined by the difference of TBN from TAN = TBN - TAN. If TBN - TAN becomes negative, oil can no longer protect against wear and corrosion, the problem becoming worse and worse with a more negative number. The more positive TBN - TAN, the better the wear protection is.

While I generally agree, the article you linked to talks about the importance of these factors in diesel engine oil. Many believe that TAN is important in diesel engine applications, but less important in gasoline engine applications. Blackstone certainly believes this.

Also, that paper was written in 1997. Nowadays we have modern oil chemistries that have fairly high starting TAN. Does that mean they can't last as long as the oils made back in the 90s? I don't think so.

Quote:

With a higher initial TBN, it will take the increasing TAN longer to reach the decreasing TBN.

That assumes that the rate of TBN depletion as well as TAN uptake of various oils is the same. Yet we know very well this isn't always the case.

Quote:

For me this is very interesting because I had thought that if TBN was above 2.0 or 3.0, it was fine. On the contrary, that's not the case at all. In fact, I worry even more now with the modern engine oils having smaller and smaller initial TBNs.

PS: Here is another good reference on oil life, also talking about other elements.

Yup. This is why Wearcheck keeps condemning my UOAs, even though my TBN was above 4. They actually use a rule of thumb that if TAN reaches 80% of TBN, they suggest the oil be changed.

Hi Quattro Pete,

I heard about some sources mentioning TAN might be more applicable for diesel engines as well. However, I am thinking that it's a myth. I would have a hard time believing it because TBN and TAN are simple, universally applying chemical concepts. Nevertheless, if there is a reason behind it, I would like to learn it.

As I just posted, starting TANs are high today due to to the ashless (nonmetal) succinimide dispersants that have been required thanks to SN/GF-5, which are acidic. SN/GF-5 has required more dispersants than in the past in order to better fight against sludge. However, on the down side, dispersants are acidic (corrosive) and they reduce the effectiveness of ZDDP, moly, and other antiwear and friction-modifier additives.

I had a misconception myself about TBN retention/depletion until I revisited the article. You can reread (2) and (5) in my original post. In reality it turns out that for a given engine and driving conditions, an oil with a faster-depleting TBN protects better against the acids than an oil with a slower-depleting TBN. This is because if some detergents, especially the Mg-based detergents, are not effective in neutralizing certain types of acids. Therefore, they will keep their alkalinity (TBN) longer. However, since they are not neutralizing certain acids, TAN will rise rapidly. So, for a given engine and driving conditions, if TBN is being depleted more slowly, it means TAN is rising more rapidly. This is not a good thing at all. It's important to avoid oils that retain their TBNs longer because this means they are not neutralizing the acids formed in the oil. Mg-based detergents in particular are not effective in neutralizing certain kinds of acids and they should be avoided. Also, Mg-based detergents seem to contribute to the base-oil oxidization as well.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3251166 - 01/17/14 12:22 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
nleksan Offline


Registered: 11/20/08
Posts: 562
Loc: Cincinnati, OH
The similarities between engine oil, and the courses regarding pharmacology of the digestive tract (in particular, antacids and the like), is striking. The basiccchemistry is pretty much the same.

Who's up for throwing some TUMS into their crankcase? wink
_________________________
00 328Ci(419rwhp/392rwtq) RL/Motul/OS Giken
06 M3 ZCP/6MT - RL
01 325i - RL/RP
03 M5 - RL
88 M6 (Eu) - RL
95 M5 (Eu) - RL

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#3251172 - 01/17/14 12:26 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Rand]
CATERHAM Offline


Registered: 11/18/05
Posts: 9582
Loc: Burlington, Ontario, Canada
Originally Posted By: Rand
you leave out key points such as detergents competing with antiwear additives etc.

Exactly.
If you want to truly minimize engine wear pick an oil with a very low TBN but with a high AW additive level (but not too high) like a dedicated race oil.
Of course be prepared for very short OCIs.

With PCMOs I prefer an oil with a lower than average virgin TBN level since I don't push my OCIs. In practise TBN is simply not a factor when selectly an oil since I prefer to keep my OCIs short based on mileage but not time.
But if one does want to maximize their OCI then establishing a base line for a given oil with a UOA including both a TBN and TAN test is what one should really do. I agree TBN alone is not enough.
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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#3251173 - 01/17/14 12:29 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Jeffs2006EvoIX]
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
Originally Posted By: Jeffs2006EvoIX
Quote:
While I generally agree, the article you linked to talks about the importance of these factors in diesel engine oil. Many believe that TAN is important in diesel engine applications, but less important in gasoline engine applications. Blackstone certainly believes this

This may be true my last UOA showed my TBN was 3.3 TAN was 5.1. According to this read M1 0w40 is killing my engine.

Though my car is gas not diesel so it must not apply? hornets

Jeff

Hi Jeff,

This discussion is getting interesting.

Let's set the TAN applies to mostly diesel engines aside for a while, as it won't contribute much to this discussion. wink

Mobil 1 0W-40 SN has a very high initial TBN and it's interesting that it still went below the rising TAN. I would really like to see your UOA results with Mobil 1 0W-40 SN versus other oils you used in your engine, including the TBNs and TANs where available. Could you link them here?

I am now starting to better understand why in addition to mileage, there is also months specified by the OEMs for the OCIs. If TAN exceeds the TBN, chances are that the oil is no good anymore. However, if you limit the months (say to six months), you could greatly limit the wear induced by the TAN exceeding TBN, as it probably happens more over time than over miles.

I am also now considering the Mobil 1 0W-40 SN for my next oil change, as the TGMO 0W-40 SN TBN is very weak.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3251184 - 01/17/14 12:45 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Gokhan]
Quattro Pete Offline


Registered: 10/30/02
Posts: 25921
Loc: Michigan
Originally Posted By: Gokhan
I would really like to see your UOA results with Mobil 1 0W-40 SN versus other oils you used in your engine, including the TBNs and TANs where available. Could you link them here?

I believe it's here:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3161668/2013_GTI_M1_0w40_UOA#Post3161668


By the way, here are mine:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2983142#Post2983142

Note the PU 5w-40 sample from 03/20/12 that had TAN exceeding TBN. Even though it was only after 6K miles and I have a 7qt sump, but the oil was in service for 16 months (spanning 2 winters). That's likely what caused TAN to spike. And that's why I cut down my OCI and now stick to annual changes. However, looking at wear metals, there doesn't appear to be an issue. Then again, a $20 UOA isn't a good wear indicator, AFAIK.
_________________________
'02 530i (PU 5W-40)
'08 C300 4Matic (M1 0W-40)
'13 F700 GS (BMW HP 15W-50)

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#3251185 - 01/17/14 12:46 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: CATERHAM]
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
Originally Posted By: CATERHAM
Originally Posted By: Rand
you leave out key points such as detergents competing with antiwear additives etc.

Exactly.
If you want to truly minimize engine wear pick an oil with a very low TBN but with a high AW additive level (but not too high) like a dedicated race oil.
Of course be prepared for very short OCIs.

With PCMOs I prefer an oil with a lower than average virgin TBN level since I don't push my OCIs. In practise TBN is simply not a factor when selectly an oil since I prefer to keep my OCIs short based on mileage but not time.
But if one does want to maximize their OCI then establishing a base line for a given oil with a UOA including both a TBN and TAN test is what one should really do. I agree TBN alone is not enough.

Certainly, the balance between the different additives is crucial.

Yes, the length of OCI is crucial in deciding which oil to use. You better have high initial TBN for long OCIs, whether it's miles or months.

Unfortunately, the real problem is the antagonism between emissions and wear. Keeping the emissions down requires lower phosphorus (ZDDP) levels because phosphorus poisons the catalytic converter. However, when you lower the phosphorus (ZDDP), you also must lower the detergents, as they reduce the effectiveness of ZDDP. When you lower the detergents, you have lower initial TBN, which increases the wear with used oil, especially for longer OCIs. Diesel engines also suffer from similar problems and there is also the diesel particulate filters, which the detergents will increase the clogging of and therefore detergent limits must be set, lowering the TBN.

So, given the forces of emissions regulations and wear protection being at constant war, it's never easy to find the right oil for a given application. Something that may work better for you may not be something what you think you must use.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3251211 - 01/17/14 01:09 PM Re: TBN, TAN, Ca, Mg, base-oil quality, oil life [Re: Quattro Pete]
Gokhan Offline


Registered: 12/29/10
Posts: 1559
Loc: Los Angeles, California
Originally Posted By: Quattro Pete
Originally Posted By: Gokhan
I would really like to see your UOA results with Mobil 1 0W-40 SN versus other oils you used in your engine, including the TBNs and TANs where available. Could you link them here?

I believe it's here:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3161668/2013_GTI_M1_0w40_UOA#Post3161668

Thanks.

Jeff's UOAs are looking OK. His engine seems to form a lot of acid in the oil. I would stick with Mobil 1 0W-40 SN, which has a strong initial TBN. I wouldn't worry about the high-SAPS and/or intake valve deposits. I would also not exceed 6 months or 6,000 miles.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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