Oil change.

"Tony Cox" wrote in message
news
You'll have to walk me through this Ron, because I still don't
get it. The flight to warm up the oil was just short of an hour.
I know that burning fuel creates some water & that it'll get into
the oil. But why am I seeing 'beading' in the old oil, but not the
fresh stuff? The only thing that can possibly be different is the
composition of the old oil compared to the new.

When my mechanic does an oil change on my plane, he
disconnects a hose...the first part to run out is pure water.

I don't have a problem with low oil temperatures either.

Paul

"Paul Sengupta" wrote in message
...
"Tony Cox" wrote in message
news
You'll have to walk me through this Ron, because I still don't
get it. The flight to warm up the oil was just short of an hour.
I know that burning fuel creates some water & that it'll get into
the oil. But why am I seeing 'beading' in the old oil, but not the
fresh stuff? The only thing that can possibly be different is the
composition of the old oil compared to the new.

When my mechanic does an oil change on my plane, he
disconnects a hose...the first part to run out is pure water.

I don't have a problem with low oil temperatures either.

Interesting. How much water? Do you specialize in short
trips? Live in a humid part of the world?

"Tony Cox" wrote in message
ink.net...
"Paul Sengupta" wrote in message
When my mechanic does an oil change on my plane, he
disconnects a hose...the first part to run out is pure water.

I don't have a problem with low oil temperatures either.

Interesting. How much water? Do you specialize in short
trips? Live in a humid part of the world?

Mmm, humid part of the world...the UK...but not near the coast.
Think it's more to do with the water generated in the burning than
that from the atmosphere.

Short trips. Usually 1-2 hours. Some of half an hour/40 minutes.

How much water? Um, not sure, but enough it see it pouring out
of the hose clear before the oil starts coming out.

Paul

"Paul Sengupta" wrote in message . ..
"Tony Cox" wrote in message
ink.net...
"Paul Sengupta" wrote in message
When my mechanic does an oil change on my plane, he
disconnects a hose...the first part to run out is pure water.

I don't have a problem with low oil temperatures either.

Interesting. How much water? Do you specialize in short
trips? Live in a humid part of the world?

Mmm, humid part of the world...the UK...but not near the coast.
Think it's more to do with the water generated in the burning than
that from the atmosphere.

Short trips. Usually 1-2 hours. Some of half an hour/40 minutes.

How much water? Um, not sure, but enough it see it pouring out
of the hose clear before the oil starts coming out.

Paul

You don't need to live in a humid part of the world to find water
in your crankcase. Water is a byproduct of combustion, and there are
always a small amount of gases escaping past the piston rings into the
crankcase. Colder weather will cause more of the vapour to condense in
the case instead of travelling through and out of the breather, as the
crankcase is cooler. Short flights or ground runs are much worse; the
oil doesn't get warm enough to boil off the accumulated moisture. If
this moisture is allowed to remain in the oil, it will react with
sulfur and chlorine compounds in the oil and produce acids which eat
the engine away from the inside. Your airplane ages even if it's not
flown.
The original poster probably saw water beading on the upper part
of the dipstick where the tube is in colder air and the vapour will
condense and stay for some time. He likely doesn't normally check his
dipstick after flights and hasn't seen this before. I've seen it
numerous times before changing oil, even after considerable flight
time. Cooler weather is the problem.

Dan

"Dan Thomas" wrote in message
om...

The original poster probably saw water beading on the upper part
of the dipstick where the tube is in colder air and the vapour will
condense and stay for some time. He likely doesn't normally check his
dipstick after flights and hasn't seen this before. I've seen it
numerous times before changing oil, even after considerable flight
time. Cooler weather is the problem.

Dan

Well, being the original poster, I *do* check the dipstick after
each flight, and this particular flight (just before oil change) and the
one before it showed 'beading' where there normally isn't any.
Further, after the oil change, flight, and further check, things were
back to normal, with the oil properly covering the dipstick.

It is conceivable that the beading could be due to an accumulation
of water over the 4 months since the oil change. I discount this
because the flights preceding the checks which revealed beading
were 4.4 and 1.5 hours respectively -- which should have been
sufficient to boil off any absorbed water, at least to the level where
the water content was not significantly different from that in the
'clean' oil after a 1 hour flight.

My gut feeling is that the difference is due to the changing chemical
composition of the oil with age.