We have large Waukasha engines that run on digester gas, our TBN keeps going down while the rest of the analysis is fine.
Is there an additive we could use to bring it back up.
Pros, Cons???????

Im curious as to what is causing the TBN depletion? Is the TBN not lasting the full service life?
Digester gas is a new one to me Im afraid. But I dont think there is a TBN only aftermarket product. Perhaps you need to adjust to a different ash content?

Sometimes it will last a while and other times it falls short of full service life. It realy has me baffled. Engine Mfg. says to change every 800 hrs. I have had it to almost 1600 hrs.
I don't know whats going on.

when the results are erratic, look at the conditions for variables. High loads can cause additional blow-by, seriously reducing the TBN. Temperatures can also cause variations.
Some oils lose their additives more quickly than others.

Tim,

Did you run TAN & Viscosity? As long as TAN,Viscosity and wear elements are normal,no need to concern about TBN.Testing TBN by different methods gives different readings.Check
with your lab guys....

Bala.

Tim,

Among the most popular gas Engine lube is the Mobil Pegasus series and you have not indicated the lube.

Most liqued fuels, particularly the poorer distaillates used in marine suffer due to higer sulphur content, than initially visualized. In Gases too the same problem would arise.

One probable route would be to check each supply of gas for the Sulphur content and make correction in the TBN of the lube oil. In short, if you are normally using a 40 TBN lube, you may need to top up with 50 TBN lube till balance or acceptable levels are met.

Hussam Adeni