So I've fallen into an information hole this morning (nerd sniped somehow, I don't remember what started it), and I ended up on the Blackstone website ordering a test kit and eventually clicked through to their Do I Need a TBN? article where it mentions this:
But I'm still at a loss for explaining the prior confusion; why do hydraulic and gear oil applications need to test for TAN as opposed to TBN? Wouldn't these applications still need a basic solution rather than an acidic one in order to prevent surface corrosion? Or do hydraulic and gear oils work differently than motor oils? Or conversely, is it the case that base additives don't matter as much in hydraulic and gear oils, and all we're really interested in is the acidity of the solution, hence the TAN test preference?
That last sentence confused me. So, googling around and using the search function here, I got to this thread:Scientifically speaking, the TBN is one of two “neutralization number” tests run on oils. The TAN (Total Acid Number), which is used for hydraulic and gear oil, is the other.
Originally Posted by SpectroScientific Background TOTAL ACID NUMBER A high concentration of acidic compounds in a lubricant can lead to corrosion of machine parts and clogged oil filters due to the formation of varnish and sludge. When a lubricant breaks down, acidic by-products will be formed...