Hydraulic Oil Sample
 

I just received the results of a hydraulic oil sample test, I took on my Skymaster. First, I didn't know that 5606 could break down in viscosity -- but according to the test it did. My records never show any oil change...only adding. The oil viscosity report recommended replacing the hydraulic fluid (so I did).

There were also significant levels of sodium and phosphorus in the oil. Does anyone know where/how sodium (salt) and phosphorus got in the oil? I thought it might be just plain old dirt; but the silicon levels were extremely low. I'm not even sure where phosphorus normally comes from either.

Any thoughts?