TBN Question

[Falcon_LS]

What is the lowest TBN reading that is acceptable to determine whether or not the current fill should stay in service?

If the TBN was 10.5 at the start, and reads 2 after 19,000 km (12,000 miles) of service, how much longer could have this oil gone? Thanks!

 

[es350]

depends on what you want..Some say <1, <2 etc..

 

[Pablo]

Depends on the measurement method as well.

 

[JAG]

Studies have shown that there is not a good certain, universal, ending TBN value or fraction of initial TBN value or simple TBN, TAN relationship. That sentence's grammar sucked...sorry.

There also may be other condemnation values reached before TBN or TAN becomes a problem.

 

[Gary Allan]

As JAG says, it's not always that simple. While I don't understand the condemnation norms, TAN levels are more important as TBN erodes. Some authorities say that when the two levels meet is when the OCI should end, but my observations of authoritative analysis say that you have to factor the whole UOA before automatically using that crossroads as a condemnation point. For all I know it's the elevation from baseline in TAN that makes the condemnation valid. If you were in a perpetual UOA program with one or two fixed spec oils, you could see the point where extending the service interval showed a "taking off" of TAN levels.

 

[hooligan24]

I found this quote on another Analysis site when I was searching for the meaning of TAN.

"As a general rule of thumb, if the TBN is measured at 2.0mg KOH g-1 or less, or if it's 50% of the virgin oil TBN, the oil is considered unfit for engine protection and there is a risk that corrosion could take place. The use of a high sulphur fuel will decrease the TBN at a faster rate due to the increased formation of sulphuric acid."

 

[Colt45ws]

I have to disagree with 50% of virgin. Lots of oils are being run to below 50%.

 

[JAG]

Originally Posted By: Gary Allan
If you were in a perpetual UOA program with one or two fixed spec oils, you could see the point where extending the service interval showed a "taking off" of TAN levels.


Yeah, with a given oil and a given engine, and a good UOA program, this could be experimentally determined.