"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.