Originally Posted By: loneryder
Clevy, that is a good question. I've only used Blackstone and don't know what other analyzers say. Who did dnewton use? You think going down to a 1 TBN is ok?
Simple answer:
I use Blackstone.
Extended answer:
There are two things to understand about the base number:
1) knowing TBN is really only half the equation; you need to know TAN as well
2) TBN/TAN are only predictors to how the oil might be viewed for continued use
Regarding point 1, if TBN is some low value (say 2) and your TAN is not at or much over that same value, then there really isn't a lot of concern for acid reactions. However, if your TBN is 2 and your TAN is 7, then you have a much more acidic condition.
Regarding point 2, both TBN and TAN are only values to predict the future viability of the lube. Just because TBN goes low and/or TAN goes high, it does not assure that massive sludge is emmient or acid errosioin is assured. These are only values to predict the potential for onset of problems. These are values that state, in effect, "Hey - pay closer attention; you're getting near some point of condemnation and wear rates may be affected soon." Certainly the base number has some relationship to the formation of sludge, but it is NOT an assurance of the formation of sludge, but rather a relative value to represent an increased risk for such.
The thing to understand is that some of the components that contribute to TBN to reduce acidity are also elements that assist in "cleaning". So, when TBN is low, there is a presumption that the cleaning capacity is reduced. I would agree with that. But it's not like low TBN is a 100% guarantee of immediate sludge. It only means that there is less capacity for cleaning up sludge as it is generated. It's not like you'll get a massive dump of sludge one day. Sludge is a condition of several factors; overt oxidation, low TBN, hot spots in the engine are all contributors. These don't just "happen"; rather, they develop over a long period. So when TBN drops, it's not like sludge is just going to clump your valve-train in the next 500 miles.
When you see TAN cross over a low TBN, it means you need to start paying closer attention, and UOA more frequently to keep a closer eye on the relationship, as well as use other tools (such as visual inspections under the valve cover) to make sure you're not in a danger zone.
Unfortunately, many here don't understand the way TBN/TAN relate to a UOA. They think, because they have been told, that a finite number is a cause for automatic condemnation. I completely disagree with that concept. They are values to give a relative status mark and help discern when closer scrutiny is due. It's really no different than some arbitrary value for an OCI. Why OCI at 5k miles? Because the OEM told you to. But that does not mean the oil and filter are anywhere near the end of their useful lifecycle? No; it's a conservative value that protects the OEM at your expense. Same goes with a low TBN; changing oil at some predetermined value is a means of simply making it "simple" for folks to understand.
In some of my extended O/FCIs, you can see that TAN crossed over TBN, and yet no sludge formed (pix posted as proof from under the valve cover) and no wear escalated (UOA values at or lower than average). The OEM O/FCI is 5k miles. In a back-to-back series, I ran a 10k mile O/FCI and then a 15k mile O/FCI on dino ST oil and with a normal filter. And yet after 25k miles of extended use, the wear continued to be low and the sludge formation was non-existent. I used enhanced UOAs, visual inspection under the valve cover, visual inspection of filter disection; all these are tools to inform me my actions were just. And they give me a basis to use extended OCIs for the future, and dial back the expenses.
A UOA (and all the info therein) is but one of many tools we have to maximize the value of the OCI. Unfortunately, most think that a UOA is a toy where the guy with the lowest wear number and highest TBN wins. Nothing could be further from the truth. The real thinking-man's interpretation goes much deeper.
(Caution - forthcoming rant about to take place
this is NOT directed at the poster or OP, but just a genearl statement)
All this leads to my seemingly bad attitude towards folks here who "play" with UOAs and under-utilize premium products. It's their money to spend as they see fit; I get that. But I have more respect for folks that simply O/FCI at OEM intervals with normal products and never give it a second thought. There are a bazillion vehicles out there that will last a lifetime with simple, routine care. It may be wasteful, but it's safe. But at least they don't double down on the waste and pay for UOAs, use expensive products, and still OEM at normal intervals. These type folks (and there are many here) are simply dabbling in a science that they clearly don't understand how to use. If one pays for a UOA, for goodness sake understand what the info is really telling you and then formulate a plan of action based upon the data you paid for. If you don't alter your operational program, when data tells you it's safe, you're heaping waste upon waste. Why pay for a syn product, a premium filter, a UOA, and then ignore the rational action plan? I just will never, ever understand that. It's not that I don't waste and over-spend; I certainly do so. But I don't try to pretend it's anything other than an emotional desire. I "want" some things that I'm willing to pay for that others see as waste. I don't try to rationalize it with some lame excuse; I own my waste and don't try to hide it. But some folks here try to justify their actions with a complete lack of understanding of the topics and/or total disregard for logic. That, I will never understand.
Thus endeth the rant.
