There is another thread going on here in which the TBN for Mobil1 is being debated. This got me to thinking and I have this question: Is the TBN value of an oil in the bottle an intinsic qualitative measure, or is the ability of the oil to buffer and maintain its TBN value that makes for a quality oil? For example, is an oil with a high TBN value necessarily a better oil? What if that value drops off dramatically under use and abuse? It seems intuitive to me that an oil that maintains its value is a better oil, even if it starts at a lower virgin value than one with a high TBN that has decremented more significantly. I speculate that an oil with a TBN of 10 that drops to 6 has performed better than one that starts at 12 and drops to 6, all other conditions being equal. Your take?