Oil Temp Sensor

[RossB]

A good synthetic oil will tolerate 200 degrees for short periods of time (mineral oil can be as low as 120 degrees) but what you have to keep in mind is that the oil temperature is not the same everywhere in the engine. The oil is at its hottest when it is in contact with the under side of the piston, on a turbo engine this is likely to be about 75 degrees hotter than the oil in the oil pump. So (depending on where you are measuring your oil temp) with readings of 150 degrees the oil could be seeing temperatures around 220 degrees. Of course oil will not fail instantly but if it is exposed to temps above 200 degrees it will break down over a period of time and its ability to lubricate the engine will degrade. Keeping the temperature below 130 degrees allows for the fact that the oil is going to be about 75 degrees hotter in parts of the engine where it is not practical to measure it. I would normally aim for 100 - 110.

I would not expect an over-rev to cause a bearing failure. Bearing failure is caused by a lack of lubrication, excessive load or in-correctly installed bearings or components.