HI Peter,
I rang Penrite, 1300 7367 483, and asked a few questions.
For what it is worth, the HPR 30 has a "flash point" of 220degress C.
The answer would be to ask what oils would perform best at a temperature, if you run the
oil at 120 degress then may be a HPR 40 would suit you better. You could run a sythetic
oil which work better at the higher temperatures.
I think I actually change the
oil every 1000kms, after a good track day it is worth changing the oil. As they say oil is cheap but engines are expensive.
Phil