TAN ?

[JimPghPA]

I posted a used oil analysis here on bitog about a year ago, and the TBN was 2. That was for GC after two years (24 months) of use and 8K miles. Someone commented that I should have also had the oil analyzed for its TAN number. And that the TAN stood for total acid number.

Now with 13 months on this oil change we have about 5.5 K miles on this fill of GC so we are chocking up miles a little faster than we did on the last OC. Therefore 8 K might happen before 24 months this time, and I would like to know if it is worth it to get a more expensive oil analysed by Blackstone instead of the $14 NAPA analysis that does not include TAN. And I do understand that the TAN might be an additional charge.

I understand that TBN is the PH of the oil and it should be on the base side indicating that the oil still has some ability to absorb acid. I also understand that a TBN of 1 is considered the minimum base number and that a TBN below 1 indicated that the oil no longer has the ability to properly neutralize acids. The oil I sent in to have analyzed had a TBN of 2 so it was approaching a TBN of 1 and was therefore a good time to change.

Someone posted that if I really wanted to know if the oil was still good that I should have had the TAN measured, and that TAN stands for total acid number.

What is TAN (total acid number) and how is it different than the TBN number. The PH of the oil is the same regardless of what it is, or what it called, so why or how does TAN differ from TBN and why is it worth paying extra to get the TAN report? What can you tell from a TAN report that you can not tell from a TBN report? And what is the minimum good number for TAN and in what direction on the scale is TAN very good, and TAN bad (such as TBN of 2 is better than TBN of 1) (TBN is better if it is higher).

I am just trying to figure out what the TAN tells about a used oil, and why it would be worth paying for.

Thanks in advance for any information regarding this.

 

[earlyre]

ok,Jim, I'm gonna give out a lot of info that you'll probably say "Well I already know THAT!" but I'm Sharing the info i came across when your question caused me to ask the same thing. maybe it answers your question, Maybe Not. Not trying to "insult your intelligence"(as my dad was fond of saying) or anything, just lend a hand to the community at large who might have similar wonderings.

http://en.wikipedia.org/wiki/Total_Base_Number
http://en.wikipedia.org/wiki/Total_acid_number
"The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. It is an important quality measurement of crude oil. The TAN value indicates to the crude oil refinery the potential of corrosion problems. It is usually the naphthenic acids in the crude oil that causes corrosion problems. This type of corrosion is referred to as naphthenic acid corrosion (NAC)."

From BlackStone's FAQ: (pay special Attention to The ATF question)
Ok, now for the technical questions. What is a TBN?

A TBN (total base number) measures the amount of active additive left in a sample of oil. The TBN is useful for people who want to extend their oil usage far beyond the normal range. To learn more, Click Here.

Do I need to send in a separate sample for a TBN?

No. We can run your TBN on the same sample of engine oil you send. It's also not necessary to send in a sample of virgin oil for a TBN. You're welcome to do so, of course, and many people do this to see where the TBN starts out. If you do send in the virgin oil sample, the cost for that sample is the same as for your used engine oil sample.


Can I get a TBN on my ATF?

Well, you could, but it wouldn't mean very much. The TBN is based on the level of calcium sulfinate and magnesium sulfinate in the oil, and transmission oil doesn't have much of it. We can, however, run a TAN (Total Acid Number) on your transmission oil.

From their "Do I need a TBN?" page, (linked to above):

"Scientifically speaking, the TBN is one of two "neutralization number" tests run on oils. The TAN (total acid number), which is used for hydraulic oils, is the other. The TBN measures how much base (as in, a base vs. an acid) additive is in the oil to offset the deleterious effects of
acids coming into the oil from combustion and other sources. "

so, on a basic Level, TAN is a measure of how acidic the oil is, while the TBN tells you how much neutralization capacity it still has...more or less...unless i completely read that the wrong way, in which case, never mind.

 

[Quattro Pete]

http://www.machinerylubrication.com/Read/2170/oil-drain-interval-tan-tbn

Also:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2428192/TAN_VS_TBN_CROSSOVER#Post2428192

 

[JimPghPA]

Earlyre, I once read a book on how to write a book, and it said that if you write a book that contains too much information that the reader already knows that the reader may become bored and uninterested, and some may even be insulted, and if you write a book that is too far ahead of the reader and you do not cover the material required to take a reader from what they know to what the book teaches that the reader will become lost in the gap of information you left out.

So knowing that, I am never going to be insulted if someone repeats information I already know. I just chock it up to me not conveying what my level of knowledge is on the subject and the writer not knowing what my level is.

It seams to me that the whole TBN and TAN are both trying to represent the PH and acid absorbing abilities of an oil, but each is coming at the problem from different angles. The TBN from the Base side, and the TAN from the acid side. Kinda like one person measuring a horses height from the left side vs a person measuring the same horses height from the right side.

 

[Donald]

Most companies that do a UOA will do a TBN for lubricants involved in combustion (engine oil) and TAN for gear oil, ATF. Why Blackstone charges extra is beyond me.

The ultimate for engine oil would be BOTH TAN and TBN and the oil should be changed when TBN intersects TAN (if both were plotted on a graph).

TAN does not start at zero, its got a slight value in a VOA. Its when it starts to move that the oil is nearing the end of its useful life.

 

[A_Harman]

Maybe it's more of a rate of change thing. If you were to measure TBN and TAN every 1500 miles and plot them, TAN would start to trend up quickly when TBN reaches some low value. This is the point at which the oil should be changed. I have read different TBN vs TAN strategies on BITOG:
1. Change when TBN equals TAN.
2. Change when TAN exceeds TBN by a few whole numbers (~4).
3. Change when the increase in TAN equals the decrease in TBN.

Why not just take pH measurements of the oil, and change at 7 (neutral)?