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

[[email protected]]

I just watched a program about the huge Oresund bridge between Denmark
and Sweden, and there was a segment about how the corrosion problem for
the bridge was dealt with. Instead of painting, they use sealed
compartments that have the air humidity kept below 60%. This they said
eliminates corrosion. This started me thinking about the corrosion we
aircraft owners are told to guard against, since I have personally been
told by an overhaul shop, that half of all the engines he sees that
need work, need it because of corrosion. There are several "facts" that
I am beginning to question as to their validity. The ones that come to
mind are:

1) You have to get the oil up to 180 deg F or the water in the oil
won't evaporate.

2) Starting and ground running the engine for a minute or so is the
"worst" thing you can possibly do.

3) Flying for an hour will "clean" the oil (or at least evaporate the
water, preventing acid formation) so that it doesn't turn to acid and
dissolve the engine while sitting idle.

There are probably some others, but these three stand out the most
to me. Now I am sure that what I am about to say will not go over well
with some people, but I have the asbestos suit ready and waiting.
My take is that these three "facts" are a bunch of poppycock. Why
or how they got started is anyone's guess, but the reasoning behind
some of them is understandable, for others I wonder what they were
smoking at the time. My thoughts are along these lines, and I admit I
could be wrong, but I don't think so.

Concerning fact #1...Why does someone think that the water has to be
brought to a boil before it will evaporate. Water evaporates very well
even at sub-freezing temperatures,much less at the warm to hot temps
created in a running engine. And at say 140 F, I can't help but believe
that any water or moisture in the engine will be purged quickly. With
water at that temp you can literally see clouds of vapor escaping, and
this is well below boiling. Not that the hotter the engine gets the
water doesn't evaporate more quickly, it does I'm sure. It's just that
in the engine cases which are open to the air at the breather tube and
elsewhere, any heat above say 85 F or so will be more that enough to
dry out the oil in the crankcase. As evidence of this, I ground run my
engine all the time and have for many years. I live in a VERY humid
climate. The oil analysis reports I have done on a regular basis by
Blackstone have never shown any trace of water or moisture. I recently
tore done the engine for rebuild after more then 15 years of perfect
service, and the cam lobes, lifter faces, and every part in the engine
was shiny and totally free from rust or any other corrosion.

Concerning fact #2.... We all constantly clean and oil many of the
things we own such as tools, etc. It is the layer of oil that prevents
the rust. I accept that if the oil is too acidic it could corrode or
"chem mill" the metal, but it takes highly acidic liquid to do that,
and the oils I use have acid buffers in them to deal with mild acidity.
Running is the only way to re-oil all the parts in the engine,
especially the cam and lifters. Just like oiling the machinists tools
that I own keeps them rust free, oiling the engine keeps it rust free I
would think.

Concerning fact #3.... This is the one that really makes me wonder. If
oil needs to be changed every 25-50 hours, how does flying for an hour
clean it? I can't help but think that the longer the oil is used the
dirtier it gets. I guess they think that it's "really" dirty just after
starting, and you "clean" it as you fly.

In closing, it seems to me that many of the things we are told are
contradictory on this subject. I have witnessed many OWT come and go in
my time, so common knowledge isn't always correct, lean of peak
operation comes to mind. Some blockheads still don't think George Braly
has it right.


Blue Skies
Rusty

[mikem]

wrote:
....
> 1) You have to get the oil up to 180 deg F or the water in the oil
> won't evaporate.

Water and oil are immisible; oil floats on water; water droplets
agregate, form globules, which sink to the bottom of the galleys and
the sump. They are effectively surrounded by oil, and the water cannot
"evaporate" because there is no way for the water droplet to reach the
air so that evaporation can take place.

When an engine is operated, the oil (and water) are heated and
homogenized, turned into a mist by the throws on the crankshaft. That
is the only time the water droplets get a chance to do the evaporation
trick, where water molecules get into the air, and can exit the
crankcase through the breather, either as visible steam, or as an
increase in relative humidity of the air leaving the crankcase.

However, the net movement of air (carrying the water mist) out of the
crankcase is propelled only by the blowby past the rings, which
contains new water as a byproduct of combustion in the cylinders which
is added to the old water already in the oil. So, it seems that the
process which removes water from the crankcase (heat, thrashing,
blowby) and the process that adds water (combustion, blowby) reach an
equilibrium.

However, if the engine oil reaches a temperature where a droplet of
water will boil, then as it does, it turns to steam, the volume
increases dramatically to where the pocket of steam will "float"
upwards through the oil, and finally burst free. This is what provides
the transport mechanism to purge the water from the oil. I dont
consider this "evaporation", rather "boiling the water out of the oil",
and yes, flying an airplane an hour a week is better than letting it
sit for months without being flown.

> 2) Starting and ground running the engine for a minute or so is the
> "worst" thing you can possibly do.

This is true on cars, for a reason that has nothing to do with the
engine or oil! It has to do with rusting out the exhaust system.
Starting the engine with a cold exhaust system and running it for a
short time means that the water that is a byproduct of the combustion
condenses onto the cold metal in the muffler and tailpipe. If you ran
the engine longer, the exhaust system would eventually heat up to the
degee that it will evaporate the water, but if you only run the engine
for a minute or two, then you will leave the exhaust full of water, so
it just sits and rusts. If you do this regularly, you will be replacing
the muffer, etc ever year or two, instead of every five to seven.


> 3) Flying for an hour will "clean" the oil (or at least evaporate the
> water, preventing acid formation) so that it doesn't turn to acid and
> dissolve the engine while sitting idle.

Never heard this one; only the "boiling water out of the oil" one.

[Dave Stadt]

"mikem" > wrote in message
ups.com...
>
> wrote:
> ...
>> 1) You have to get the oil up to 180 deg F or the water in the oil
>> won't evaporate.
>
> Water and oil are immisible; oil floats on water; water droplets
> agregate, form globules, which sink to the bottom of the galleys and
> the sump. They are effectively surrounded by oil, and the water cannot
> "evaporate" because there is no way for the water droplet to reach the
> air so that evaporation can take place.
>
> When an engine is operated, the oil (and water) are heated and
> homogenized, turned into a mist by the throws on the crankshaft. That
> is the only time the water droplets get a chance to do the evaporation
> trick, where water molecules get into the air, and can exit the
> crankcase through the breather, either as visible steam, or as an
> increase in relative humidity of the air leaving the crankcase.
>
> However, the net movement of air (carrying the water mist) out of the
> crankcase is propelled only by the blowby past the rings, which
> contains new water as a byproduct of combustion in the cylinders which
> is added to the old water already in the oil. So, it seems that the
> process which removes water from the crankcase (heat, thrashing,
> blowby) and the process that adds water (combustion, blowby) reach an
> equilibrium.
>
> However, if the engine oil reaches a temperature where a droplet of
> water will boil, then as it does, it turns to steam, the volume
> increases dramatically to where the pocket of steam will "float"
> upwards through the oil, and finally burst free. This is what provides
> the transport mechanism to purge the water from the oil. I dont
> consider this "evaporation", rather "boiling the water out of the oil",
> and yes, flying an airplane an hour a week is better than letting it
> sit for months without being flown.

How does that work for an automobile engine which is a closed system?

>
>> 2) Starting and ground running the engine for a minute or so is the
>> "worst" thing you can possibly do.
>
> This is true on cars, for a reason that has nothing to do with the
> engine or oil! It has to do with rusting out the exhaust system.
> Starting the engine with a cold exhaust system and running it for a
> short time means that the water that is a byproduct of the combustion
> condenses onto the cold metal in the muffler and tailpipe. If you ran
> the engine longer, the exhaust system would eventually heat up to the
> degee that it will evaporate the water, but if you only run the engine
> for a minute or two, then you will leave the exhaust full of water, so
> it just sits and rusts. If you do this regularly, you will be replacing
> the muffer, etc ever year or two, instead of every five to seven.

12 years, 235K miles and still the original exhaust system.

[mikem]

Dave Stadt wrote:

> 12 years, 235K miles and still the original exhaust system.

But I bet you drive it at least 3 mi each time you start it.

[[email protected]]

Very well stated.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ben
www.haaspowerair.com

[Dave Stadt]

"mikem" > wrote in message
oups.com...
>
> Dave Stadt wrote:
>
>> 12 years, 235K miles and still the original exhaust system.
>
> But I bet you drive it at least 3 mi each time you start it.


That's true most of the time but it still doubles your estimate for muffler
life.

How about the moisture in auto engines without crankcases vented to the
outside world? How does it get out? Once it floats upward and bursts free,
as you say, where does it go? Don't hear about auto engines with corrosion
problems even collector cars that are only driven a couple of times a year.

[[email protected]]

Dave Stadt > wrote:

> "mikem" > wrote in message
> oups.com...
> >
> > Dave Stadt wrote:
> >
> >> 12 years, 235K miles and still the original exhaust system.
> >
> > But I bet you drive it at least 3 mi each time you start it.


> That's true most of the time but it still doubles your estimate for muffler
> life.

> How about the moisture in auto engines without crankcases vented to the
> outside world? How does it get out? Once it floats upward and bursts free,
> as you say, where does it go? Don't hear about auto engines with corrosion
> problems even collector cars that are only driven a couple of times a year.

All crankcases are vented somewhere.

Usually to the intake manifold through the PCV valve in modern cars.

--
Jim Pennino

Remove .spam.sux to reply.

[M]

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.

[mikem]

Crankcase fumes are sucked into the induction manifold (and burned by
passing through the engine) via the Postive CrankCase Ventilation check
valve.

[Drew Dalgleish]

Running an engine on the ground is bad. It's boring and wastes gas
just go do some circuits to get the oil warm.

[Dave Stadt]

> wrote in message
...
> Dave Stadt > wrote:
>
>> "mikem" > wrote in message
>> oups.com...
>> >
>> > Dave Stadt wrote:
>> >
>> >> 12 years, 235K miles and still the original exhaust system.
>> >
>> > But I bet you drive it at least 3 mi each time you start it.
>
>
>> That's true most of the time but it still doubles your estimate for
>> muffler
>> life.
>
>> How about the moisture in auto engines without crankcases vented to the
>> outside world? How does it get out? Once it floats upward and bursts
>> free,
>> as you say, where does it go? Don't hear about auto engines with
>> corrosion
>> problems even collector cars that are only driven a couple of times a
>> year.
>
> All crankcases are vented somewhere.
>
> Usually to the intake manifold through the PCV valve in modern cars.

Which is a closed loop. So how does the moisture escape?

>
> --
> Jim Pennino
>
> Remove .spam.sux to reply.

[Dave Stadt]

"mikem" > wrote in message
ups.com...
> Crankcase fumes are sucked into the induction manifold (and burned by
> passing through the engine) via the Postive CrankCase Ventilation check
> valve.

The question still remains....how does the moisture escape as modern engines
are not vented to the atmosphere but are a closed loop. We aren't talking
about crankcase fumes but about moisture supposedly being boiled off into
the atmosphere.

[[email protected]]

Drew Dalgleish wrote:
> Running an engine on the ground is bad. It's boring and wastes gas
> just go do some circuits to get the oil warm.

What proof is there that it is bad? And sometimes weather and
circumstances don't allow people to fly. I believe that ground running
is better than bare metal corroding. My engine would have been corroded
a long time ago if the oil from a ground run would do that, and it
hasn't been.

Blue skies,
Rusty

[mikem]

But its not a closed loop. An auto engine operates at temperatures up
to 235 degF because of the pressurized cooling system. Water in the oil
boils and steam escapes from the oil. The PCV system effectively sucks
the moisture laden air, steam, and oil droplet mist in the crankcase
into the intake manifold. It gets mixed with other air that came
through the air cleaner and fuel, gets compressed in the cylinders,
goes bang, and >95% of it goes out the exhaust pipe. Only a tiny
fraction leaks back into the crankcase as a result of blowby...

The process reaches an equilibrium with very little residual water in
the oil. When the engine is stopped and cools, that is when the water
content of the oil is the lowest.

[soxinbox]

I think that several people have tried to make this clear. The oil warms up
and water evaporates out into the crankcase. the PCV valve allows the water
vapors to be sucked from the crankcase into the intake manifold. It is mixed
with the intake air goes through the cylinder and pumped out the exhaust. It
is not a closed system since the vapors are free to exit the motor via the
exhaust ( while running ).

"Dave Stadt" > wrote in message
. com...
>
> "mikem" > wrote in message
> ups.com...
>> Crankcase fumes are sucked into the induction manifold (and burned by
>> passing through the engine) via the Postive CrankCase Ventilation check
>> valve.
>
> The question still remains....how does the moisture escape as modern
> engines are not vented to the atmosphere but are a closed loop. We aren't
> talking about crankcase fumes but about moisture supposedly being boiled
> off into the atmosphere.
>

[soxinbox]

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.
>

[Private]

"Dave Stadt" > wrote in message
. com...
>
> "mikem" > wrote in message
> ups.com...
>> Crankcase fumes are sucked into the induction manifold (and burned by
>> passing through the engine) via the Postive CrankCase Ventilation check
>> valve.
>
> The question still remains....how does the moisture escape as modern
> engines are not vented to the atmosphere but are a closed loop. We aren't
> talking about crankcase fumes but about moisture supposedly being boiled
> off into the atmosphere.

'Modern' engines (with PCV for POSITIVE Crankcase Ventilation) are NOT a
closed loop. The atmosphere from the crankcase is sucked into the intake
manifold by engine vacuum (then burned in the engine), the atmosphere sucked
out of the crankcase is replaced by filtered air (either from a breather or
engine intake air filter) and blowby gases. Usually an attempt is made to
induce some cross flow such as by sucking air out of one end (or side) of an
engine and replacing it in the other. This ventilation is maximum at closed
throttle (low manifold pressure) and minimum at full throttle (high manifold
pressure).

AFAIK most aircraft use the older type of crankcase ventilation system
utilizing (what in an automobile was called a road draft tube) a tube cut at
an angle and extended into the airstream to create a lowered pressure. This
system only functions when the tube is in moving air, and on the ground this
is only supplied by the prop wash and is significantly less than the flow
occurring when actually flying. This is also part of the reason that
actually flying is far superior to ground running for removing moisture from
the crankcase.

Happy landings,

[[email protected]]

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

[[email protected]]

Mikem,

You make some good points. The main issue I have is simply whether it
is better to run the engine and oil the parts, or just let it sit.
Someone posted that where they live, that many times flying is not an
option for weeks at a time. I completely agree that flying for an hour
or so weekly is the best thing, but I have had times during the winter
when short days and drizzly crappy weekends have made getting in the
air dangerous when my schedule has allowed it. I know what the effect
of moist air against bare metal does. What does the coat of oil from a
ground run do to the metal? I seriously doubt if it is as bad. I would
like to know if anyone has actually measured the acidity or moisture
content of the oil in such an instance? As I stated, my oil analysis
always shows no moisture; none! And I ground run the engine alot.
Glad to hear your comment about the exhaust system issue. I
wouldn't be surprised if the advice about not running the engine up to
temp on a car for this reason, was the beginning of the advice not to
do the same for airplanes. I wonder what it does for our mufflers given
they are designed differently. Those puppies get hot quick!
It would be a shame to trash an engine trying to save an exhaust! ;).

Rusty

[David Lesher]

"Dave Stadt" > writes:


>> Crankcase fumes are sucked into the induction manifold (and burned by
>> passing through the engine) via the Positive CrankCase Ventilation check
>> valve.

>The question still remains....how does the moisture escape as modern engines
>are not vented to the atmosphere but are a closed loop. We aren't talking
>about crankcase fumes but about moisture supposedly being boiled off into
>the atmosphere.

They most surely are vented. They have an air intake & an exhaust
pipe. The PCV system sucks any *crankcase* fumes into the intake
so as to burn them in the combustion cycle. So as the oil gets hot
and boils the water vapor out, it gets sucked into the intake side...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[[email protected]]

>Water evaporates very well
>even at sub-freezing temperatures


Sublimates that is.....

Rusty

[[email protected]]

Dave Stadt > wrote:

> > wrote in message
> ...
> > Dave Stadt > wrote:
> >
> >> "mikem" > wrote in message
> >> oups.com...
> >> >
> >> > Dave Stadt wrote:
> >> >
> >> >> 12 years, 235K miles and still the original exhaust system.
> >> >
> >> > But I bet you drive it at least 3 mi each time you start it.
> >
> >
> >> That's true most of the time but it still doubles your estimate for
> >> muffler
> >> life.
> >
> >> How about the moisture in auto engines without crankcases vented to the
> >> outside world? How does it get out? Once it floats upward and bursts
> >> free,
> >> as you say, where does it go? Don't hear about auto engines with
> >> corrosion
> >> problems even collector cars that are only driven a couple of times a
> >> year.
> >
> > All crankcases are vented somewhere.
> >
> > Usually to the intake manifold through the PCV valve in modern cars.

> Which is a closed loop. So how does the moisture escape?

Are you serious?

The intake manifold goes to the combustion chambers which goes to the
exhaust manifold which goes to the exhaust pipe.

--
Jim Pennino

Remove .spam.sux to reply.

[Capt. Geoffrey Thorpe]

> wrote in message
oups.com...
>
> Drew Dalgleish wrote:
>> Running an engine on the ground is bad. It's boring and wastes gas
>> just go do some circuits to get the oil warm.
>
> What proof is there that it is bad? And sometimes weather and
> circumstances don't allow people to fly. I believe that ground running
> is better than bare metal corroding. My engine would have been corroded
> a long time ago if the oil from a ground run would do that, and it
> hasn't been.
>
> Blue skies,
> Rusty
>

One of the things we (at an auto company) have to do is make sure that cars
cold start well. And, nowadays, we even have to meet emission regulations at
lower temperatures. Now, the problem is that it's hard to get a lot of cold
starts into a short period of time. So, what to do? One technique is to use
cold fluids (water, oil, even air) to force cool an engine and get multiple
cold starts per day. When some dynomometers were set up to do cold start
after cold start, we started to grenade the engines in short order - largely
due to oil dilution from gasoline - you get some in the crank case with
every start and if you don't warm up, it builds up. Moisture from blowby
builds up too. Repeated short starts are, in general, not a good thing. What
you propose isn't nearly as severe, but short, repeated runs are not likely
to get you to the maximum TBO.

There's nothing magic about 180 degrees - but the warmer it is, the higher
the vapor pressure from the water, and the more it dries out. Aircraft
engines are at a bit of a disadvantage since they still just use a breather
tube so the only "air" going into the crankcase is from the blowby which is
loaded with water and CO2 (all engines have blowby - it's just a question of
how much). The positive flow from the PCV system on cars has been shown to
increase the longevity of the engines, but just sticking one on an aircraft
engine won't have the same benifit since aircraft run at high manifold
pressures (little or no vacuum) for extended times so you wouldn't get much
flow from a PCV so all you can do is warm it up enough and run it long
enough for things to dry out.

Oil needs to be changed because the long chain hydrocarbons break down and
viscosity changes. Also, there are a lot of additives for friction and wear
reduction, foam supression, etc. that tend to break down. Carbon particles
are not a problem for gasoline engines since there is almost no soot
generated. Diesel's on the other hand, make lots of soot, and some of it
makes it's way into the oil.

If you really want to circulate some oil, crank without starting . If you
want to run it, run it long enough to warm up. Short runs aren't an instant
disaster, but they really aren't what you want to do for a long TBO.

But, it's your engine...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[soxinbox]

One reason for not running a car or airplane for short periods is that you
have initial startup wear. Most of the wear in cars, and perhaps airplanes
too, happens at startup, when there is zero oil pressure, minimal oil on the
surfaces, and the presence off some condensed moisture. If you could only
run an engine on the ground for 5 minutes at a time, you would definitely
not want to run it once a day. On the other hand running it like this 4
times a year would probably increase the life by making sure there is some
oil on the interior surfaces. I don't know of any data that will tell us
where the sweat spot is that causes the least wear. One point of evidence we
do have is that engines that are not run for extended times do corrode in
tell tale ways. You never want to buy a plane that has sat for extended
periods.

> wrote in message
oups.com...
>I just watched a program about the huge Oresund bridge between Denmark
> and Sweden, and there was a segment about how the corrosion problem for
> the bridge was dealt with. Instead of painting, they use sealed
> compartments that have the air humidity kept below 60%. This they said
> eliminates corrosion. This started me thinking about the corrosion we
> aircraft owners are told to guard against, since I have personally been
> told by an overhaul shop, that half of all the engines he sees that
> need work, need it because of corrosion. There are several "facts" that
> I am beginning to question as to their validity. The ones that come to
> mind are:
>
> 1) You have to get the oil up to 180 deg F or the water in the oil
> won't evaporate.
>
> 2) Starting and ground running the engine for a minute or so is the
> "worst" thing you can possibly do.
>
> 3) Flying for an hour will "clean" the oil (or at least evaporate the
> water, preventing acid formation) so that it doesn't turn to acid and
> dissolve the engine while sitting idle.
>
> There are probably some others, but these three stand out the most
> to me. Now I am sure that what I am about to say will not go over well
> with some people, but I have the asbestos suit ready and waiting.
> My take is that these three "facts" are a bunch of poppycock. Why
> or how they got started is anyone's guess, but the reasoning behind
> some of them is understandable, for others I wonder what they were
> smoking at the time. My thoughts are along these lines, and I admit I
> could be wrong, but I don't think so.
>
> Concerning fact #1...Why does someone think that the water has to be
> brought to a boil before it will evaporate. Water evaporates very well
> even at sub-freezing temperatures,much less at the warm to hot temps
> created in a running engine. And at say 140 F, I can't help but believe
> that any water or moisture in the engine will be purged quickly. With
> water at that temp you can literally see clouds of vapor escaping, and
> this is well below boiling. Not that the hotter the engine gets the
> water doesn't evaporate more quickly, it does I'm sure. It's just that
> in the engine cases which are open to the air at the breather tube and
> elsewhere, any heat above say 85 F or so will be more that enough to
> dry out the oil in the crankcase. As evidence of this, I ground run my
> engine all the time and have for many years. I live in a VERY humid
> climate. The oil analysis reports I have done on a regular basis by
> Blackstone have never shown any trace of water or moisture. I recently
> tore done the engine for rebuild after more then 15 years of perfect
> service, and the cam lobes, lifter faces, and every part in the engine
> was shiny and totally free from rust or any other corrosion.
>
> Concerning fact #2.... We all constantly clean and oil many of the
> things we own such as tools, etc. It is the layer of oil that prevents
> the rust. I accept that if the oil is too acidic it could corrode or
> "chem mill" the metal, but it takes highly acidic liquid to do that,
> and the oils I use have acid buffers in them to deal with mild acidity.
> Running is the only way to re-oil all the parts in the engine,
> especially the cam and lifters. Just like oiling the machinists tools
> that I own keeps them rust free, oiling the engine keeps it rust free I
> would think.
>
> Concerning fact #3.... This is the one that really makes me wonder. If
> oil needs to be changed every 25-50 hours, how does flying for an hour
> clean it? I can't help but think that the longer the oil is used the
> dirtier it gets. I guess they think that it's "really" dirty just after
> starting, and you "clean" it as you fly.
>
> In closing, it seems to me that many of the things we are told are
> contradictory on this subject. I have witnessed many OWT come and go in
> my time, so common knowledge isn't always correct, lean of peak
> operation comes to mind. Some blockheads still don't think George Braly
> has it right.
>
>
> Blue Skies
> Rusty
>

[mikem]

Good Post, Captain!