Hey Ken,

That was what I tried to say. Obviously I was not successfull.

A good synthetic like Mobil 1 can handle sustained temps over 300F for hours. Amsoil or Redline can do the same among others. Mobil 1 in particular handles high temperatures very well.

At what oil temperature do the rubber seals start to become damaged?

As mentioned before I run Amsoil in my 29' Fountain with a 500 EFI, in Havasu with ~110* ambient temp and have never seen my oil temp above 180*. As mentioned the synthetics can sustain much higher temps.

Don't know but that is a good question! lol

If you've never seen above 180 for oil temps, then you are not getting the moisture out of the oil either. Need to get to 212 minimum..........

There are two "oil temperatures". One is the oil temperature coming out of the engine/crankcase. The other is the oil temperature coming out of the oil cooler/returning to the engine. Blue motors are set up to record the oil temperature returning to the engine after being cooled by the oil cooler....so I am told. 180F is typical of oil temperature after the oil cooler. The oil temperature of oil coming out of the engine/crankcase is that associated with 220F and above...300F and beyond depending on HP and oil cooler efficiency.

I was speaking in general of oil temps, not taking into account of where the oil temp sensor is. But thank you for enlightening me.

Measured in the pan, 280 deg. will blacken Mobil 1 15-50 in an hour. I wouldn't run any oil to 300 deg. Oil temp and oil pressure gages will help yor engines to live long and happy lives.

Kurt, oil sample shipped out today.

I will post the results when I get them.

Ken