Lower detergent levels but more cleanliness?

[SonofJoe]

The two commonest (aka cheapest!) forms of overbased detergent additive used in PCMO are 300 TBN calcium sulphonate & 400 TBN magnesium sulphonate. I did a quick bit of Googling and the former contains about 12% Calcium and the latter 9.2% Magnesium (note that only the pure metal part of the additive shows up on a UOA or VOA).

So to get a boost of 1 TBN, you need 0.33% of 300 TBN Calcium Sulphonate which is equivalent to 0.0396% (or 396 ppm) of Calcium metal. To get the same 1 TBN boost, you need 0.25% of 400 TBN Magnesium Sulphonate which is equivalent to 0.023% (or 230 ppm) of Magnesium metal.

So if an oil formulator, faced with passing an LSPI test, part replaces Calcium detergent with the same class of Magnesium detergent but still keeps the same overall oil TBN, then the overall content of metal in the oil will go down.

I never looked but I would not say that Magnesium has any better TBN retention properties than Calcium. What you want from a detergent is something that mops up acid (derived from the oxidation of base oil) as soon as said acid is formed. The whole concept of TBN 'retention' is IMO deeply flawed because it's a way of pretending that inefficient detergents (notably overbased salicylates) are 'good' when in reality they are 'bad'.

 

[Shannow]

SoJ,
Is that why some analysts spec the "TBN TAN" crossover point as the condemnation limits ?
(Sorry if it's not a sensible question, I'm out of any league on these...not even in the stadium maybe).

 

[weasley]

^^^All of this^^^

TBN retention is a red herring. Elemental analysis as a proxy for detergency is a red herring. "Boron" being bandied about as a thing is a red herring. There is so much under the surface that can change how an oil behaves that a VOA and UOA simply won't pick up.

 

[weasley]

Originally Posted By: Shannow
SoJ,
Is that why some analysts spec the "TBN TAN" crossover point as the condemnation limits ?
(Sorry if it's not a sensible question, I'm out of any league on these...not even in the stadium maybe).


I've gone on record here as stating that I don't believe that TAN/TBN crossover is a meaningful condemnation limit, other than that it is conveniently easy to see. The units of TAN and TBN are highly derivative and almost arbitrary; there's no reason to believe that when TAN>TBN that something fundamental has changed with the oil. It's not like pH.

 

[Shannow]

And again,
UOA is an oil serviceability/condemnation tool
VOA gives you something to measure changes against

B$tone are making a fortune out of mugs who think they can compare oil x and oil y with 3ppm of iron...I did my UOA on my first new car back in 2006 as it came out of warranty to ensure that there wasn't anything catastrophic like a coolant leak that I could hold Nissan on the hook for.

 

[Shannow]

Originally Posted By: weasley
Originally Posted By: Shannow
SoJ,
Is that why some analysts spec the "TBN TAN" crossover point as the condemnation limits ?
(Sorry if it's not a sensible question, I'm out of any league on these...not even in the stadium maybe).


I've gone on record here as stating that I don't believe that TAN/TBN crossover is a meaningful condemnation limit, other than that it is conveniently easy to see. The units of TAN and TBN are highly derivative and almost arbitrary; there's no reason to believe that when TAN>TBN that something fundamental has changed with the oil. It's not like pH.


Thanks...back when I worked in power transmission, I knew the transformer oil tests and reasons (and effects on other things like copper corrosion and paper degradation)...just never got into it on engine oils.

 

[weasley]

Originally Posted By: Shannow
And again,
UOA is an oil serviceability/condemnation tool
VOA gives you something to measure changes against

B$tone are making a fortune out of mugs who think they can compare oil x and oil y with 3ppm of iron...I did my UOA on my first new car back in 2006 as it came out of warranty to ensure that there wasn't anything catastrophic like a coolant leak that I could hold Nissan on the hook for.


Agreed. However when you do a UOA TBN using ASTM D4739 and compare it to a VOA (or PDS) value of TBN using ASTM D2896, you've already lost a significant portion of TBN just through the method difference.

Oil should be condemned on a holistic approach, with all factors looked at. Of course if one factor is grossly wrong then by all means condemn, but if TAN>TBN but the absolute TBN is still quite high and wear metals and viscosity are under control, condemn...?

 

[Virtus_Probi]

BITOGer wemay posted a link to a paper that suggested that magnesium-based detergents tended to interfere with the MoS2-ZDDP synergy that formed a protective "glass" on hot metal surfaces, but that boron-based dispersants could help this layer form properly in the presence of said detergents.

I wonder if this was a reason for predominance of calcium-based detergents in pre-d1G2 oils (excepting a some M1s, T6 5W40, and some Edges at times)...I think it's worthy of note that calcium is not completely eliminated from d1G2 oils, it's just present in generally reduced levels.

I am basically parroting back some stuff I read and didn't completely understand here, I would beg anybody who really knows this stuff to chime in and correct any misunderstanding on my part!

 

[Shannow]

Originally Posted By: weasley
Oil should be condemned on a holistic approach, with all factors looked at. Of course if one factor is grossly wrong then by all means condemn, but if TAN>TBN but the absolute TBN is still quite high and wear metals and viscosity are under control, condemn...?


Posting order has got the conversation skewed...Following your statement on TAN/TBN, certainly no...

 

[SonofJoe]

The TBN-TAN crossover method for condemning oils goes way, way back. At some point in history, when DI packs were simple 3-way affairs and all oils were Group I based (and as such were very easily oxidised to complex carboxylic acids), then the methodology, for all of its inconsistencies, might have made sense but today? I think not.

The bigger issue of course is when exactly do you condemn an oil and why? It seems to me that from a technical point of view, the answer for most PCMO's today is 'too soon'! I read BITOG and still see some folks changing their oil when it starts to 'go dark' or adhering to the '3,000 miles or every three months' rule (even if they're on full synthetics) and I truly despair! All that work & effort to improve motor oil quality seems totally in vain! Even the European rule of getting your oil changed every year at the annual service is for many people far too restrictive. By way of example, the wife's car had barely done 2,500 miles when it was time for its 25,000 mile annual service!! (BTW, the service was needed to preserve the warranty).

But what's the alternative? According to the industry standard Sequence IIIG test, an oil is 'condemned' when you exceed 150% viscosity increase. Yet no sane person would run their oil out to such a limit! All of the tests used by industry to assess oils are now so far divorced from automotive reality as to tell you nothing meaningful as to when to change your oil!

My own personal view is that most modern reputable PCMOs, provided that their Noack isn't excessive, are good to go for 10,000 miles of 'normal' service & that includes fully formulated Group I oils. Most synthetics, I'd say are good for 12,500 miles. I personally wouldn't advocate going much beyond this, not because the oil won't technically function but because the risk vs reward balance favours changing the oil.

BTW, agree with Brother Weasley that focussing on Boron is wholly wrong. Unless things have changed since I went away, Boron in engine oil derives primarily from Boric Acid capped Ashless Dispersants and as such, could be argued to be a 'bad' thing.

 

[SonofJoe]

Originally Posted By: Virtus_Probi
BITOGer wemay posted a link to a paper that suggested that magnesium-based detergents tended to interfere with the MoS2-ZDDP synergy that formed a protective "glass" on hot metal surfaces, but that boron-based dispersants could help this layer form properly in the presence of said detergents.

I wonder if this was a reason for predominance of calcium-based detergents in pre-d1G2 oils (excepting a some M1s, T6 5W40, and some Edges at times)...I think it's worthy of note that calcium is not completely eliminated from d1G2 oils, it's just present in generally reduced levels.

I am basically parroting back some stuff I read and didn't completely understand here, I would beg anybody who really knows this stuff to chime in and correct any misunderstanding on my part!



I don't doubt for a second this is what this group of researchers found. However, based on a lot of direct & relevant experience, I would categorically refute that Magnesium-based detergents interfere with protective surface layer formation or impact negatively on wear.

It's a long time ago now but I remember well when I was advocating Magnesium (as a simple cost cutting exercise), people were queueing up to tell me why I was wrong! Magnesium caused bore glazing. It caused water miscibility problems. Apparently the Japanese hated it so much they banned its use in motor oils (that is until LSPI reared its head and then it was the best thing since sliced bread!). Wrong! Wrong! Wrong!

 

[Garak]

SonofJoe, it would seem to me, at least in the HDEO realm of things, that magnesium became a lot more evident in those when CJ-4 came out and we saw the 1.0 SA limit, too, especially with those that were E7, E9, requiring both the higher starting TBN and the 1.0 SA at the same time.

 

[JAG]

Lower sulfur in fuel allows less detergent to be necessary and I think dispersants are therefore relied on more so for cleanliness. Good/excellent antioxidants are important too because oil oxidation by-products are also a source of acids, besides the fuel combustion acids. Of course base oils affect cleanliness as well. Due to the high cost of Group V oils, formulators of the major motor oil companies tend to not use them or use just a small amount. The thermal and oxidative stability of them tends to be high and being polar, they provide a detergency credit. They can dissolve/suspend deposit precursors.

Start at page 26, here: https://www.atc-europe.org/public/Docume...%20Benefits.pdf
Quote:
Ashless dispersants have longer hydrocarbon tails than the detergents but function similarly in that they form micelles which trap deposit precursors such as soot or sludge. Particles up to about 50nm (cf. 20nm for detergents) can be stabilised by the thicker adsorbed film. Dispersants which contain an ionisable polar head (for example succinimides) can also stabilise larger particles by charge repulsion. An ashless dispersant micelle can attract and hold at least ten times more sludge particles than a detergent micelle. Their effectiveness is shown in Figure 12. Ashless dispersants are also highly effective at stabilising soot produced by diesel engines, preventing particle agglomeration and hence oil thickening.
Dispersant viscosity modifiers are ashless too, but have a higher molecular weight. They form even thicker barrier films by attaching themselves to particles at several points and can stabilise particles up to about 100nm.

 

[SonofJoe]

Originally Posted By: Garak
SonofJoe, it would seem to me, at least in the HDEO realm of things, that magnesium became a lot more evident in those when CJ-4 came out and we saw the 1.0 SA limit, too, especially with those that were E7, E9, requiring both the higher starting TBN and the 1.0 SA at the same time.


You're quite right, if you're restricted on Sulphated Ash, you get more TBN bang with Magnesium than you do with Calcium. If it wasn't for the fact that it's highly toxic, I'd probably be advocating the use of Beryllium as the basis of very high TBN, low ash detergents.

 

[Virtus_Probi]

Originally Posted By: SonofJoe

I don't doubt for a second this is what this group of researchers found. However, based on a lot of direct & relevant experience, I would categorically refute that Magnesium-based detergents interfere with protective surface layer formation or impact negatively on wear.

It's a long time ago now but I remember well when I was advocating Magnesium (as a simple cost cutting exercise), people were queueing up to tell me why I was wrong! Magnesium caused bore glazing. It caused water miscibility problems. Apparently the Japanese hated it so much they banned its use in motor oils (that is until LSPI reared its head and then it was the best thing since sliced bread!). Wrong! Wrong! Wrong!


This is really interesting info, thank you so much!
Amazing to me that magnesium was cheaper but not used much because of a lot of myths. At least XOM has been on the magnesium bandwagon for a while.