2010_FX4,
I also use Amsoil's Severe Gear Gear Lubes, although I use the 75W-90. In my 2006 Tundra, I also use the Slip-Lok Additive from Amsoil because I experienced chatter without it. On one UOA, after about 37K miles, I performed a UOA with Blackstone and it measured 10.7! This is much higher than I have seen on any other UOA with Gear Lube. I wondered whether it had anything to do with the Slip-Lok additive. I emailed Amsoil about this, and received this reply:
Quote:
The condemnation level for TAN is when it reaches 4x the original value for the product. I have asked our lab to verify the TAN for Slip-Lok additive so we can gauge the effect of adding 8 ounces, but since SVG already contains the Slip-Lok additive, I do not expect the additive to make a major contribution to the TAN results you received in your analysis.
Usually the TAN will increase slowly during the useful life of the product, but the level shown in your analysis is unusual, especially at less than 37,000 miles of use. I looked up possible reasons for increases in acid numbers with the following result:
The AN test is performed on nonengine oil samples and is used to quantify the acid buildup in these oils. An increased AN is a result of oxidation of the oil, perhaps caused by overheating, overextended oil service, or water or air contamination.
Depending on what lab performed the analysis, you may be able to contact them to see if the test results can offer more information about why the TAN was so high. Some labs will also re-test a sample to verify unusual results.
If the TAN is verified at 10.7, the lubricant is very near the end of its service and you should consider replacing it in the near future.
I think a conservative condemnation level would be twice the virgin level, or in your case, about 6.2.
