Varies depending on where the temperature is recorded. In petrol (gasoline) engines, the top piston ring
can expose the motor oil to temperatures of 160 °C (320 °F). In diesel engines the top ring can expose the oil to temperatures over 315 °C (600 °F).
Elsewhere for obvious reasons, its less.
A friend of mine runs a land rover / range rover specialty repair shop. Based on his experience, they are capable of stopping anywhere, anytime, at any cost.
I don't know about the brakes, only their unreliability.