Appropriate temp range for Slipperential?

[simplechamp]

Just like the title says, what is a reasonable temp range for the Slipperential to get to by the end of a run? Or to put it this way, what temperatures can silicone oil withstand before breaking down?

I feel like my Slipperentials are getting a bit hot (hottest was 200F) at the end of a run. This is with relatively thick oil and medium to tight slipper settings. No excessive slip or unloading.