Grey cream in my oil tank
When I changed my oil (900 hours on 912 ULS, last did 50 hours ago), I have been suprised to see some grey cream at the end of the plug:

Then, I decided to open the oil tank to clean it:

I found kind a cream, 1-2 mm depth, smooth.; So I clean it with a paper:

The oil filter has been open: nothing. The magnet plug nothing neither. Last cleaning of the oil tank has been done 200 hours ago (some litlle standard deposite at the bottom; nothing to do with that grey cream). I fly with no leaded gas. My motor run absolutly normal (Pressure, temps, start...)
-Any idea where that could from?
Thanks in advance.