This car is gently driven, but 80% city. 142,000 miles. 14,500 miles interval, zero make-up oil added.
This uoa should be a cautionary tale regarding only the use of TBN and also blackstone's arbitrary 1.0 condemnation point. TBN only indicates the oil's potential to neutralize acids. Acid number is what quantifies the actual acid buildup which is what it's all about.
The starting oxidation number for M1 is pretty high so this can't be used at face value. And XOM says to use TAN rather than Oxidation for synthetic oils (for their products at least).
TBN vs. TAN threshold, there doesn't seem to be clear consensus. Polaris/Oil Analyzers say 65% TBN depletion or 2x starting TAN or 23 + starting oxidation. Cummins says TBN TAN. I've seen other sources say starting TAN + 3.
Starting TBN of this oil is 8-9. I've seen TAN of 2.5 (from Blackstone but I don't fully trust their testing accuracy), but the TAN was 1.7 on one of my previous uoa's.
In any case, I'll probably send a reference sample for VOA before the next UOA on this car. Viscosity is still under control so it's not at a critical level, but copper is slightly elevated. I will probably back it off to 13k miles next time.
This uoa should be a cautionary tale regarding only the use of TBN and also blackstone's arbitrary 1.0 condemnation point. TBN only indicates the oil's potential to neutralize acids. Acid number is what quantifies the actual acid buildup which is what it's all about.
The starting oxidation number for M1 is pretty high so this can't be used at face value. And XOM says to use TAN rather than Oxidation for synthetic oils (for their products at least).
TBN vs. TAN threshold, there doesn't seem to be clear consensus. Polaris/Oil Analyzers say 65% TBN depletion or 2x starting TAN or 23 + starting oxidation. Cummins says TBN TAN. I've seen other sources say starting TAN + 3.
Starting TBN of this oil is 8-9. I've seen TAN of 2.5 (from Blackstone but I don't fully trust their testing accuracy), but the TAN was 1.7 on one of my previous uoa's.
In any case, I'll probably send a reference sample for VOA before the next UOA on this car. Viscosity is still under control so it's not at a critical level, but copper is slightly elevated. I will probably back it off to 13k miles next time.
Last edited: