is this oil change over-ex?tbn 7.8 virgin-2.2 used

[jorton]

In the UOA forum one report shows TBN 2.2 for a conventional oil that starts at TBN 7.8. Is this oc over-extended?

 

[Colt45ws]

No.

 

[unDummy]

It depends.

TBN is just one number to look at when determining an interval.

So, you can have a TBN of 10 and the oil could be spent because of shearing, fuel, oxidation, moisture, soot, insolubles, or wear metals.
Or, you can have a TBN of 1 and not have any issues.

Each lab has their own way of testing TBN. So, make sure that the UOA/VOA come from the same lab.

ZDDP depletion isn't measured in a typical UOA. Some reading here: http://www.practicingoilanalysis.com/art...oup=Lubrication
http://www.noria.com/learning_center/cat...oup=OilAnalysis