TBN

[aquariuscsm]

What exactly is TBN in layman`s terms? I know it stands for "total base number",but that`s about it. Does a higher TBN always mean a higher quality oil? I`ve searched the topic a lil and it looks like most dinos are between 7.5-8.5. Mobil 1`s HM oils I`ve read are 14,and I`ve seen some Amsoils that are 12.

So what exactly does TBN mean in terms of oil quality?

 

[Quattro Pete]

In simple terms, TBN describes the amount of additive package available to fight acids in the engine. However, TBN on its own doesn't tell the whole story. It's the relationship between TBN and TAN that also needs to be looked at.

 

[Steve S]

Usually a higher TBN oil is designed for longer service life. I does not necessarily make it [higher TBN] better in all uses.

 

[Doug Hillary]

Hi,
aquariuscsm - The TBN tells more about the "chemical structure" of the lubricant rather than its "quality". It is a Lab test measurement of the lubricant's alkalinity and its ability to neutralise acid. The TBN typically falls is use and the TAN is essentially the reverse measuring acidic buildup

In the past a high TBN was actually counterproductive as it usually meant a higher SA level. Very high ash levels can meam increased component wear in some engine families and it can be a "barrier" to wear in others

TBN can range from 7 or so to 17 and beyond. These are mostly driven by angine type/family and application

Generally today the TBNs are lower than say a decade ago due to different chemical structures meeting various outcomes

 

[INDYMAC]

I like Doug's answer. But I'd like to add that you can evaluate the effectiveness of a formula using TAN to see how well it actually does neutralize harmful acids (not organic acids) by doing UOA's. But you will need a VOA of the oil you're using to act as a baseline. I think you'll be surprised to find that a formula that starts with a 6-7 TBN sometimes keeps acids in check better than a formula starting at 10-12 TBN for your application and OCI interval.