Does indeedy sound a little cooler than I would have expected, and had on previous cars, but not got me temp connected yet on the cos, I know I used to see a steady 90C on the 4i, with 130C when giving it a bit, your temp is plenty enough to protect well though, but if still unsure I would contact oilman, to see about ideal temps.
I also found as you did with the castrol, both with the older rs and the newer stuff, so stopped using it.
tabetha