If you put too much oil in an engine it will heat up the engine more
because the crankshaft hits the extra oil and causes the oil to be
flung around and this also leads to oil foaming.
Extra heat is generated by flinging the oil around and the bearings
don't get enough oil since the pump does not pump foam well.

A oil quality gauge would be nice but it would add weight and cost. A
simple float switch set at 4 quarts would be nice and should not cost
much?

The old radial's used to have oil tanks that held 5 or 10 GALLONS.

If you really want to know how much water is returned to your engine
by the M20 route the oil return to a quart catch bucket for a few
hours. Then look at the contents of the bucket. One good test is
worth a thousand expert opinions!

I have found over the years that my O320 likes to run at 7 quarts. If
you fill to the max 8 quarts it uses that 8th quart in about 2 hours.
I did discover an interesting effect last month. I normally use a
quart in 4 to 5 hours. By flying at 8000 to 14000 feet for 41 hours
on a trip I only used 2 quarts in 41 hours. Since I was running wide
open throttle I had no engine manifold vacuum most of the time. It
would appear to me that the extra oil usage at part throttle was
caused by the oil being sucked down the intake valve guides.
Someone more knowledgeable may comment on this.

On Sun, 15 Aug 2004 02:44:50 GMT, "Jay Honeck"
wrote:

Air/Oil Separators do seem to perform their intended function with a
minimum of problems (when installed correctly, anyway), but my mechanic
recommended I NOT install one because they return moisture to the case
that would normally be vented overboard with the oil vapor. The
long-term effect is reportedly the same as if you were to run the engine
for short periods without attaining the operating temperature required
to boil off the water -- namely, corrosion.

Thanks for the comments, Doug. I had not heard this, and my mechanic did not
mention it, but I suppose it makes some sense.

On the other hand, since I fly every few days, I find it hard to imagine
that moisture could build up (or even survive) a flight with CHTs in the 350
degree range, and EGTs in the 1500 degree range!

There is also something to be said, IMHO, for adding oil between oil
changes. Oil breaks down over time, and throwing in a quart every 5-10
hours replenishes the anti-wear/anti-corrosion additives as well as
increases the oil's natural ability to hold contaminants in suspension.

Well, I change my oil around 25 hours minimum, 50 hours maximum. Hopefully
the billion-dollar-a-quart semi-synthetic Aeroshell oil holds together at
least THAT long before breaking down?

Also, I have found no hard evidence that keeping the oil topped vs. 1 or
2 quarts down provides any additional cooling or anti-wear properties.

I have no hard evidence either, but since oil flow is an important part of
cooling an air-cooled engine, I have to believe that having 50% more oil in
the engine is going to improve cooling performance. It also follows that
having 50% more "clean" oil flushing through the engine should keep
everything internal just that much shinier?

This is no surprise, really, as the O-360 certainly doesn't *need* six
or eight quarts of oil. I know of one application (the Seminole) in
which it is certified to run on as little as 2 quarts.

Well, yes and no. While Lycoming SAYS it's okay to run them down to 2
quarts (or even less), it is nevertheless true that engine cooling will be
hurt by low oil quantities. Sometimes less is more; in this case, only
more is more.

As an adjunct to this discussion, you've got to wonder why aircraft engines
are designed so that in the event of a leak you won't know you're out of oil
until the last pint drains out.

The oil gauge on our engines reads pressure -- not oil capacity. As a
result, you can have a major oil leak and you will not know it until those
last few ounces vent overboard -- and THEN your oil pressure gauge drops to
zero. We recently had a local Skyhawk pilot lose an oil line in flight, and
he did not know he was in trouble until his oil pressure gauge finally
dropped to zero -- at which point the crankcase was already empty, and he
was frying his engine. (He made it to an airport, but destroyed the
engine.)

What baffles me is that no one has come up with an oil QUANTITY gauge like I
have in my Mustang. This would have given the aforementioned pilot an extra
five or ten minutes to get that plane down, BEFORE he had ruined a $16K
engine.

Anyone know?

Lastly, FWIW, my partner's other airplane (a 182) has a M20 installed.
Yes, its belly is largely free of oil residue, but it still seems to
acquire a dry, chaulky residue in any case. It looks and feels like
something you'd find just aft of an exhaust stack, and may very well
result from the exhaust...

Oh, I'm sure I'll have some exhaust stains to clean -- but at least I
(hopefully) won't have that slimy belly (with dirt and grass embedded in it)
to clean off.