Water's vapor pressure rises with temperature, if you remember your
physics. Raising the vapor pressure drives it of sooner. It doesn't
have to boil. 180 is a recommendation. Below that, the water might form
in the case faster than it will evaporate, and you'll have increasing
amounts accumulating in the engine.

The research is there. Here are some who have experience in the
area:
http://www.sacskyranch.com/corrosion.htm

http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/JOM-0505-54/$FILE/JOM-0505-54F.pdf?OpenElement

http://www.ramaircraft.com/Maintenan...mendations.htm

http://www.memagazine.org/backissues...italsigns.html

Lots more if you Google it.

Dan

I hope you're just baiting me on this one, but you've left the door too
wide open, and I have to go through it just once. I read all four of
the web sites that you posted, and frankly I don't really see where you
might think that any of them deal with the issue that I thought we were
talking about by giving specific data on a comparison basis. You know,
like stating the moisture content and acidity of sample A is such and
such and from sample B it is such and such. So I'll comment on them one
by one.

Sacramento sky ranch...... This page shows pictures of rusted (not
dissolved or corroded by acid) lifter faces and such and talks about
how important it is to guard against it and how quickly it can occur.
It gives the same advice that we have been talking about, the
importance of frequent flights, oil changes, etc. I don't see where it
gives a comparison of oil moisture content or acidity for oil sampled
from frequently flown aircraft versus that sampled from engines that
were only ground run. Do you? If so please tell me where. We all
understand that oil eventually drains off engine parts and the moisture
in the air will cause it to rust. I thought we were discussing whether
or not oil deposited from a ground run-up would protect the cam or
corrode it, right? Like I said, many places say that you must fly often
to evaporate the moisture, but samples from each with numbers showing
how much the moisture and acidity increases to detrimental levels when
you only ground run the engine have been hard to find.

Website #2.... This is an article where a comparison of the corrosion
resistance of two different magnesium alloys is presented. I think it
best to quote a part of the article here.
From the article:
"The internal corrosion response
concentrates solely on the behavior of the alloy within the coolant
circiut of the engine."

That's means they're looking at how a new alloy's corrosion
performance compares to an old one when exposed to anti-freeze. They
didn't even consider the oil circulating through the block. Probably
because they know it doesn't corrode things but protects them. I don't
see how they answered any of our questions. The cases on my Lyc are
made from A356 aluminum, and the cam and lifters from steel and iron.
The corrosion response of a magnesium alloy to anti-freeze relates to
the corrosive effect of oil from a ground run on a camshaft just how
Dan?

website #3....RAM Aircraft....This is just mostly the same stuff as
what was on the Sac sky ranch site. Mostly good advice, but certainly
nothing that demonstrates with scientific data that oil from a ground
run has such and such moisture content and PH level. They did however
demonstrate that knowledgeable people can have different opinions. From
the article,
[RAM service history records indicate that Mineral
Based AD oils perform significantly better than synthetic and
semi-synthetic oils.]

I see that you have had better results from Aeroshell Semi-Synthetic,
.

website #4....This article talks about new devices being developed that
are beginning to monitor in real time the chemical condition of the oil
in an engine. Didn't see data giving a comparison of the moisture
content or PH of frequently run oil versus that from a ground run here
either. Like I've said, maybe some people have done it, but I haven't
seen it published. These devices will sure make that possible though.
Maybe we will see something in the future! Yea!

I really don't think that anyone would think that those sites gave good
scientific data that supported the opinion that ground runs will
corrode your engine, but every year there are several forced landings
with fatalities, due to engine failure that would not have happened had
the engines not been allowed to rust. Maybe those engines would have
been saved had someone not been told to just let them sit if you can't
fly them. That is why I felt I should respond. After all, the ONLY
scientific data I have seen on the subject is my own oil analysis
results that told me there is 0.0% moisture in my oil sample.

I ground run maybe 6 or so times during the winter, in between flights
that is, and only when flying is not safe.

Blue skies,
Rusty