XDrive Transfer Case Fluid DIY

[JCL]

That is a major shortcoming.

Their recommendation to change the fluid appears to be based on a comparison with an average that doesn't mean much, if anything.

They are selling these tests based on fear, IMO.

The presence of wear metals in microscopic quantities in the oil does not require a change of fluid, as they suggest. If you left the same fluid in, and took four or five samples of that same fluid, over the same interval, then a change in the rate of wear metal increase would indicate something. It would tell you about the component, which is more valuable than trying to discern something about the fluid. But simply having the trace metals in the fluid shows nothing.