TBN=0 what happens?

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Assume a Grp II+ or better oil. So let's say the engine oil hits TBN=0 - so, what's next? If the TBN gets to zero, then I'm assuming it was an acid balance that got it there - but with a grp II+ there are essentially no nitrates or sulfates in the oil to form acid - so is it all coming from combustion products? And I don't understand this TAN thing - acidic level of the oil. (??) Not sure how TBN and TAN coexist. And what's the ramifications of TBN=0? I read once (somewhere official I'm pretty sure) that TBN=0 doesn't necessarily mean any thing for engine components (but this is probably a matter of context). And even the stoutest oils often seem to drop like a rock from their lofty levels of TBN=12 to a TBN=3 and then level off. Now what's that about?
 

ericthepig

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If anyone has knowledge on even one of the questions above, plse give input. I'm especially interested in how a grpII+ could ever become acidic in the first place.
 
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 Originally Posted By: ericthepig
Assume a Grp II+ or better oil. So let's say the engine oil hits TBN=0 - so, what's next? If the TBN gets to zero, then I'm assuming it was an acid balance that got it there - but with a grp II+ there are essentially no nitrates or sulfates in the oil to form acid - so is it all coming from combustion products? And I don't understand this TAN thing - acidic level of the oil. (??) Not sure how TBN and TAN coexist. And what's the ramifications of TBN=0? I read once (somewhere official I'm pretty sure) that TBN=0 doesn't necessarily mean any thing for engine components (but this is probably a matter of context). And even the stoutest oils often seem to drop like a rock from their lofty levels of TBN=12 to a TBN=3 and then level off. Now what's that about?
What is your screen name on the Mazda forums?
 
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I have never seen 0. At this point the detergency of the oil would be gone and I would assume deposit formation rapidly accmulate. That would also mean much of the antiwear components in the oil are no longer functioning and wear would increase. TAN and TBN can coexist. They are differnt lab test that measure differnt reactions. TAn is supposed to be the better tool for measuring oil life while TBN indcates active additive.
 
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As I understand it once TBN reaches 0 the oil has become acidic and may attack interal components. TBN isn't liner. It doesn't matter what it starts out as long as it stays above 1.
 

ericthepig

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 Originally Posted By: djquik1
What is your screen name on the Mazda forums?
Heck, I don't know. Probably ericthepig - I don't huant those places (probably should make time for it though) - I think I am a member on a Mazda 323 forum of some sort - was on there last year posting my '88 323 for sale.
 

ericthepig

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I'm starting to study UOAs in reference to TBN. Basically brooding on Schaeffer's relatively low starting TBN and M1 EP's high number (these two are neck & neck in competition for my next 1 yr OCI on the Mazda 6). It's seems to be voodoo. I've now seen both of them get shredded down below 2 (TBN<2.0) in relatively short time in good engines. Other times, they hold well above that. But from some other readings (iirc it was a M1 white paper of some sort - been years though), it sounds like it really doesn't matter as long as you don't push them way, way past what they can do.
 
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From Wikipedia. Not that I think wikipedia is an accurate place for information but this sounds about right. Total Base Number (TBN) is a measure of a lubricant's reserve alkalinity. It is measured in milligrams of potassium hydroxide per gram (mg KOH/g).[citation needed] TBN determines how effective the control of acids formed will be during the combustion process. The higher the TBN, the more effective it is in suspending wear-causing contaminants and reducing the corrosive effects of acids over an extended period of time. The associated measurement ASTM D2896 and ASTM D4739-06 generally range from 6-80mg KOH/g in modern lubricants, 7-10mg for general automotive use and 10-15 for Diesel operations. Marine grade lubricants generally will run from 15-50mgKOH/g, but can be as high as 70 or 80mg KOH/g as is the case of Exxon’s MobileGuard 570 or respectively Castrol’s Cyltech 80AW this high level is designed to allow a longer operating period between changes, under harsh operating conditions. When the TBN is measured at 2mg KOH/g or less the lubricant is considered inadequate for engine protection, and is at risk for allowing corrosion to take place. Higher sulfur fuel will decrease the TBN faster due to the increased formation of sulfuric acid. TAN (Total Acid number) is the inverse measurement of TBN. It is covered under ASTM D 664 and refers to the level of acid contamination caused by combustion.
 
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JHZR2

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Tbh doesnt necessarily tell the whole story - "TBN retention", or buffeting capacity, I suppose, is important too - how fast or slow TBN drops.
 
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I haven't figured out the interactive part of them yet, but when TAN exceeds TBN metal etching appears to increase. Oxidation appears to relate to it in some loose way too (TAN).
 
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