Should you get TAN in UOA?

[Ayrton]

I have another couple UOA on their way to Blackstone, so I wanted to ask: should I add TAN to them?

How valuable does everyone find getting TAN in addition to TBN?

If the oil wasn't pushed to its limits in mileage, should I just pass on the TAN?

Thanks!

 

[Lead Shoes]

If your goal is to stretch the oil to its limit, then you want to know the TBN and TAN to see how much farther you can go with the oil.

To determine if you should pay the extra we need to know more...

What car, what oil, how many miles/months it was in use. knowing those three would help a lot.

 

[dparm]

Yes, because it will make the TBN information more valuable.

Just because your oil had a high TBN when it was analyzed doesn't always mean it could've gone longer.

 

[Quattro Pete]

But is there consensus out there as to what level of TAN and what relationship of TAN to TBN signifies that an oil is spent? And does it directly translate into more wear easily visible on a $20 UOA? The UOA results I've seen are fairly inconclusive, to say the least.

 

[Jim Allen]

Ayrton: On a normal or not a massively extended interval, my opinion is, no, you don't ned a TAN.

Quattro Pete: I know what you are saying but there is "consensus" and there is "truth." "Consensus" can be incorrect because all it requires is agreement between parties, not truth or data.

Forgive me for being pedantic.

There are several technical references (previously discussed where you were present) that illustrate the TBN/TAN relationship and how you can make a reasonably accurate guess about TAN via the TBN. Those sources seem to have it backed up with an awful lot of data. I'm unsure enough to test thsi for myself the next few times to see but what I have read makes sense to me.

 

[Solarent]

This article is from 2008 but still represents the prevailing opinion on TBN and TAN levels. Basically when one meets the other then the oil is finished.

Corrosive wear isn't going to necessarily manifest itself in any type of elemental analysis - which means you won't see it in your Wear Metals section of your UOA. The same can be said about surface fatigue. However in a typical gas passenger vehicle you aren't going to have this problem nearly as quickly as say sludging of the motor by running extended drains.

For the OP: if you are looking to compare the TBN/TAN of various oils in your engine to help choose the "best" one or if you want to extend your oil life to the nth degree then shell out the extra money. If you suspect that the oil is expiring earlier than anticipated (I use significant changes in viscosity as an indicator) then it might be good to get the TBN and TAN. If you get one over a "normal" OCI and your TAN is higher than the TBN you may have issues that are causing extra acids to form (such as a coolant leak or water contamination). Although some labs will give you information without TAN/TBN that could be indicators of coolant or water contamination.

 

[btanchors]

I agree with several of the points made in this thread so far...In fact, I have noticed TANs appearing in more of the UOAs being posted to this board lately.

I've always obtained TANs for gear oil and ATF, but I have recently made the decision to get both TAN and TBN for my UOAs on motor oil, for one of my vehicles.

We've all seen countless TBNs already - we know how TBN behaves across a wide variety of vehicles, service environments, and oil types. But we don't have nearly as much data (at least, posted on this board in the form of UOAs) that include TAN.

In some recent VOAs I have had performed, I have been rather surprised at how high TAN starts out for some of the oils I am using - I recently had a VOA come back with a starting TAN of 4.8. I'm very interested in seeing how this holds up, in comparison to TBN, over time.

Based on papers I have read, I do agree you can go without TANs in most cases, but I am curious, particularly with the high starting TANs on some of the synthetics I am using.

 

[Radman]

Originally Posted By: Solarent
This article is from 2008 but still represents the prevailing opinion on TBN and TAN levels.


I do agree with the information from Polaris. The optimum time for a change is when the TBN & TAN meet. However Blackstone thinks a TBN of 1.0 is perfect. UOA's seem to be a game with members trying to reach TBN 1.0 as the goal. Last time I posted of this subject it became a very heated discussion.

 

[chubbs1]

Originally Posted By: Quattro Pete
But is there consensus out there as to what level of TAN and what relationship of TAN to TBN signifies that an oil is spent? And does it directly translate into more wear easily visible on a $20 UOA? The UOA results I've seen are fairly inconclusive, to say the least.


+1, Looking at the UOA's w/ TBN+TAN, many seem to defy the rule of the two meeting at an equal level equal end of oil life. There are UOA's that clearly show TAN much higher than TBN but the engine seems to be in very good shape. There also is the argument that the UOA is not that clear anyway on your engines wearing life.

Short answer: spend the money on TBN and a particle count to get a clearer picture of engine wear and life of oil.

 

[OldCowboy]

I question using TAN vs TBN as a measure of an oil's exhaustion. While Polaris notes that TAN rises above remaining TBN at approximately 65% exhaustion of TBN, they do not flag gasoline engine oils as exhausted until TBN drops to 2.0.

Additionally, they provide no data to show increased wear after TAN crosses TBN.

If you are concerned about changing oil at the TAN/TBN crossover, just change your oil when the TBN is 65% exhausted and save a couple of bucks.

 

[Solarent]

Further to my previous post - I agree with what OldCowboy is getting at - The flag of TBN vs TAN should not be the only consideration when looking at a UOA; I would say the same thing about wear metals, additive depletion and viscosity change (oxidization/sheering) when running a UOA program it is more about the trend in your engine than the specific numbers. Even VOA can sometimes give you differing results on the same oil for some trace elements.

If it is something you are concerned about track it; if you aren't too worried then don't - barring some other issue most of us don't run oil drains long enough to have it cause any significant problems.

 

[Loobed]

[opinion]
TBN is only good if you plan to expend your drain interval, or are using your engine in adverse conditions (construction, emergency electrical generator, etc). All API ILSAC oils should be able to last the vehicle manufactures recommended drain interval. If it doesn't, it is most likely the fault of the vehicle manufacturer for designating the wrong drain interval. The extra cost to get the TBN could be used for an oil change.

[/opinion]