Water in our oil, or just alot of hot air?

Although I agree the only way to ensure a healthy engine life is
frequent flying and frequent oil change, I somehow thinks that 180F oil
temp thing is an urban myth. If you have a plane that flies twice a
week for one hour each, getting oil change every 25 hr, and the oil
temp never gets above 160F due to an oil cooler that's a bit too
effective, I don't see any evidene that such an engine will be any more
prone to corrosion than a similarly operated engine with oil temp at
180F.

Even if you have your oil temp at 180F cruising at 7500, the temp will
drop quite a bit once your start the descend. Does it mean you will
collect a lot of water in your crankcase right after you pull back the
power? My point is it's meaningless to be obsessive about the 180F.
Just go fly often, and change the oil frequently.

Well stated. The temperature of the oil is measured at only one place. The
temperature of the oil varies greatly within the engine. It is probably
hottest when it leaks off the cylinders. It is coolest exiting the oil
cooler. A reading of 180 or 160 might mean that oil is above the boiling
point at many points inside the engine. Also with the oil being atomized by
the slinging in the crankcase, water will evaporate at a good rate while
below the boiling point. I would love to see some scientific data on the
evaporation rate vs. oil temp.


"M" wrote in message
oups.com...

Although I agree the only way to ensure a healthy engine life is
frequent flying and frequent oil change, I somehow thinks that 180F oil
temp thing is an urban myth. If you have a plane that flies twice a
week for one hour each, getting oil change every 25 hr, and the oil
temp never gets above 160F due to an oil cooler that's a bit too
effective, I don't see any evidene that such an engine will be any more
prone to corrosion than a similarly operated engine with oil temp at
180F.

Even if you have your oil temp at 180F cruising at 7500, the temp will
drop quite a bit once your start the descend. Does it mean you will
collect a lot of water in your crankcase right after you pull back the
power? My point is it's meaningless to be obsessive about the 180F.
Just go fly often, and change the oil frequently.

soxinbox wrote
Also with the oil being atomized by
the slinging in the crankcase, water will evaporate at a good rate while
below the boiling point.

Bravo Sir! Brilliant! Even at 1500 rpm, there is a hurricane of wind
in the crankcase that would make Katrina seem like a Summer breeze. And
at 60-90 psi of oil pressure, the oil is being pumped through the
engine like a firehose. Who said it is just sitting in the bottom of
the pan?

I would love to see some scientific data on the
evaporation rate vs. oil temp.

So would I!

Rusty