Originally Posted By: dgunay
I wouldn't extend it, TAN is already higher than TBN.
Originally Posted By: DuckRyder
It doesn’t really have any significant short trips, aside from the fact it sometimes gets backed out and pulled right back in to get the trashcan down to the curb it gets warm when it leaves the house, it is over 10 miles round trip to anything and usually it is multiple anythings when it goes to town.
I believe we decided ALS/Blackstone did TBN by different methods which usually results in approximately a point variation.
It’ll probably be over 10,000 by the year mark, but no way will it make 20,000 in a year (probably take 2) I knew this going in and fully intended to exceed the year “expiration date”... I’m not quite ready to panic over the TAN.
Overkill explained TAN/TBN to me here in this post. (more info than you need but I thought I'd post it all) Like dgunay stated/alluded to, I'd likely dump it now rather than thinking about extending it.
No way, imo, is this oil good to go for 20,000 miles as it looks like it has reached its usable life already.
TBN = Total Base Number - it is the amount of base in the oil. This number starts out reasonably high, usually around 8-9 for a PCMO, it can be higher for an HDEO. This represents the oil's ability to neutralize acids. As this takes place, that number decreases, as there is less reserve; less base, left in the oil to perform that function.
TAN = Total Acid Number - This is how much acid is present in the oil. This number starts out extremely low and, as the oil remains in service, being polluted with combustion byproducts, blow-by gasses, which include sulphuric acids and the like, may start to creep up as the base used to neutralize the acids is depleted.
Generally, there was/is an old adage that stated that once TBN and TAN crossed, the oil was no longer serviceable. However, for certain oils with certain base stocks, that may not apply, but generally it is a good rule of thumb.
Now, as per what SOJ touched on, the TBN exists due to the presence of basic compounds which are part of the overall additive package. These products can vary blender-to-blender and also in effectiveness. Certain bases aren't necessarily ideal for neutralizing certain acids, so you can end up with uptick in TAN without the corresponding depletion in TBN, which is what SOJ was saying and why you can't just glance at TBN and always assume "I'm good!". Because you might not be. Now if you have TAN, like I did in my above reports, you can see that TAN is very low in both UOA's where it was provided, and there was a pretty decent difference in TBN between the two runs as well. In either instance the oil was still suitable for use based on those numbers, but the Petro-Canada Duron-E would have required changing sooner than the Mobil product based on what appears to be the trend.
TBN and TAN together, work to establish one of the parameters for an oil's suitability for continued use. They define a set of condemnation points that, if reached, require the oil to be changed. Other parameters are wear-metal uptake, nitration, oxidation...etc. There is a reasonably decent list. This stuff can be extremely useful for expensive heavy use industrial equipment with large sumps where a periodic sample can be shipped off to Toromont or similar and evaluated to provide a snapshot of that machine's health and whether the oil is reaching the end of its serviceability. These are typically trended over the life of the machine and are monitored not only for the health of the lubricant, but also for anomalies that might suggest something amiss in the machine that warrants further investigation.