Higher TAN Good or Bad?

[DCRamsey]

I’ve got a question about TAN. I’ve had four UOA’s done by Wear Check and they measure TAN and not TBN for gasoline engines. I’d prefer to have both so I can measure the relationship between the two, but what I’ve got is TAN. Over the past four analysis, I’ve has TAN of 1.24, 2.46, 1.26 and 3.47. The last TAN was 175% increase over the previous analysis. The UOA’s were done over a similar mileage. My question is: Is a higher TAN over a similar interval good or bad. The last UOA was Eneos Sustina, so I’m wondering whether it neutralized more acid or if it’s a bad sign.

 

[Quattro Pete]

I use wearcheck and I always ask them to measure both TBN and TAN. I think it's $5 extra to have both tested.

Generally, as the oil is put in service, TBN decreases and TAN increases. Low TBN is bad, and high TAN is bad as well. Where the two values cross is usually the condemnation point, but that's just a very rough rule of thumb. However, without knowing these values for a fresh oil (VOA), it's really impossible to say whether a given TAN is high or low. Some new oil formulations have pretty high starting TAN (3+).

Then you'll also hear opinions that in a gasoline engine, TAN doesn't really matter and that one should only go by TBN.

 

[A_Harman]

It's weird that Wearcheck won't do TBN. I get my oil analyses done at Polaris, and they will only do TBN, not TAN.

 

[Quattro Pete]

Originally Posted By: A_Harman
It's weird that Wearcheck won't do TBN.

It sounds like miscommunication between OP and Wearcheck. Wearcheck will do TBN, or TAN, or both, depending on what you ask for.

http://www.wearcheck.com/mob-2-supplementary-mobile-oil-analysis-test-kit/