As can be seen from the subject line this came from the Flysoob list.
It seemed appropriate to re-post it here as the subject was just mentioned.
While not definitive, I am really surprised and encouraged at the results.
Maybe TCM does know what they are talking about when they said not to worry about oil temps. of 235F deg.
My oil cooler door has been on the shelf since the second hour of flight.

---------- Forwarded Message ----------
I didn't ask Ashland if the 350F was one minute or all day long.     
I decided to try an oil smoke test.

Four different oil samples were placed in a toaster oven.     The
heat was dialed up in 25F increments. The samples stayed at each temp
for one hour.    The heat was then turned up another 25 and the
process repeated.   This test lasted nine hours, start to finish.

The four oils were;  Mobil One 15-50,  Valvoline Racing 20-50,  
Castrol GTX 20-50 and Aero Shell 100W Plus.    This list is in the
order that I thought would withstand the smoke test, best to
worst.    The results surprised me.   Below is the results, worst to
best.

The Castrol started a light smoke, less than a lit cigarette, at
300F.    More smoke and a darkening color at 325F.    With increasing
smoke and darker in color the sample was removed from the test at
350F.

Valvoline Racing held off till 375F before starting a light smoke and
slight darkening .    At 400F and with more smoke and getting darker,
I removed it from the test.

Mobil One at 375F had a slight darkening.   A slight whiff of smoke
started at 400F.    A light smoke and a bit darker started at
425F      At 450F  the sample was removed from the test with a little
more smoke than a cigarette, plus the color was getting darker.

AeroShell amazed me in how well it held up.    I saw no reaction
until the AeroShell reached 425F where it started to discolor and
give off light smoke.    At 450F  the sample was removed with a
little more smoke than a cigarette, and getting darker.

The above test was only a smoke test.   I have no idea if the oil
molecules were losing the ability to lubricate as the temp
increased.     After the samples cooled they all looked as if they
had been in a car for 1,000 miles.

Russell Sherwood
Houston, TX




--- In FlySoob@yahoogroups.com, prolorus@... wrote:
>
>
> In a message dated 12/13/07 9:52:21 AM, sherwood@... writes:
>
>
> >
> > Interesting little fact:
> > Lycoming , at least on the O-360, measures the oil temp after the
> > oil has passed through the cooler...not in the pan
> >
>
>
>
> ............ and probably starts to molecularly disassemble.   
>Ashland says its Valvoline Racing Oil can withstand up to 350F, but
>if it were kept at 340deg how long would it last and be a good lube?
>Mental image: skillet with overly-hot oil smoking and stinking.





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