dirty oil

The oil in my Lyc. O-360 F1A6 is black only two hours after being changed.

What could be causing this? Compressions were in the 70s at annual in
September.

--
Dan
C172RG at BFM

Sounds like some serious blow-by into the crankcase. If you don't have an
oil separator on the breather, I would expect also to see a very dirty
belly. How about having a mechanic re-check the compression and look at
the inside of the cylinders?

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

I'm a uniter, not a divider. - GWB, 1999.

"Dan Luke" wrote in message
...
The oil in my Lyc. O-360 F1A6 is black only two hours after being changed.

What could be causing this? Compressions were in the 70s at annual in
September.

--
Dan
C172RG at BFM

Dan Luke wrote:
The oil in my Lyc. O-360 F1A6 is black only two hours after being changed.

What could be causing this? Compressions were in the 70s at annual in
September.

Have you changed the TYPE of oil, by any chance? Going from a mineral
based AD oil (like Phillips XC) to a semisynthetic (like Exxon Elite or
Aeroshell), can flush out deposits that have been accumulating for a
long, long time. If so, things will improve with further oil changes,
but you may want to change the oil and filter again soon.

Rip

That is true when going from a non detergent oil to a detergent oil.
Phillips XC is an ashless dispersant oil, as are most aviation oils.
Only the straight mineral oil (ie. break-in oil) is not an AD oil. I
don't think avaition oils are considered detergent oils. Marvel
Mystery Oil is effectively a detergent oil and can loosen deposits
that have built up. Word is MMO works if you use it from the start of
an overhaul run to keep valves from sticking. If you put it in an
engine with 1000 hrs on it, you risk the danger of loosening the
deposits that have built up, and possibly blocking small oil
passsages.

Bud


On Jan 28, 3:44 pm, Rip wrote:
Dan Luke wrote:
The oil in my Lyc. O-360 F1A6 is black only two hours after being changed.

What could be causing this? Compressions were in the 70s at annual in
September.Have you changed the TYPE of oil, by any chance? Going from a mineral
based AD oil (like Phillips XC) to a semisynthetic (like Exxon Elite or
Aeroshell), can flush out deposits that have been accumulating for a
long, long time. If so, things will improve with further oil changes,
but you may want to change the oil and filter again soon.

Rip

Definitely have an A&P borescope that engine. Broken ring maybe. Good
catch.

Regards,
Bud

On Jan 28, 7:02 am, "Dan Luke" wrote:
The oil in my Lyc. O-360 F1A6 is black only two hours after being changed.

What could be causing this? Compressions were in the 70s at annual in
September.

--
Dan
C172RG at BFM

"Rip" wrote:


Have you changed the TYPE of oil, by any chance?

Nope. Aeroshell W100 Plus, same as always.

--
Dan
C172RG at BFM

wrote:

Definitely have an A&P borescope that engine. Broken ring maybe.

Talked to my mechanic this morning. He said not to worry; the dirty oil is
from the oil cooler and its plumbing, which don't get drained when the oil is
changed.

He said I would have noticed this before if I had ever checked it two hours
after a change. Since I check the oil before every flight, it seems I would
have noticed the oil's turning black this soon before.

Should I pay to have the cylinders 'scoped?

--
Dan
C-172RG at BFM

On Mon, 29 Jan 2007 13:49:26 -0600, "Dan Luke"
wrote:


wrote:

Definitely have an A&P borescope that engine. Broken ring maybe.

Talked to my mechanic this morning. He said not to worry; the dirty oil is
from the oil cooler and its plumbing, which don't get drained when the oil is
changed.

He said I would have noticed this before if I had ever checked it two hours
after a change. Since I check the oil before every flight, it seems I would
have noticed the oil's turning black this soon before.

Should I pay to have the cylinders 'scoped?

Your mechanic's comment sounds unrealistic. I have a hard time
believing the 1/2 quart in the cooler & lines could add enough
coloration to the 7-8 quarts of new/clean oil.

Further, I don't notice my oil turning black until many hours after
the change. (Lyc O-360 using Aeroshell 15W50), and I never flush the
cooler during a change.

Is your oil a dark black? Or just a tinge of coloration?

On Mon, 29 Jan 2007 13:49:26 -0600, "Dan Luke"
wrote:


wrote:

Definitely have an A&P borescope that engine. Broken ring maybe.

Talked to my mechanic this morning. He said not to worry; the dirty oil is
from the oil cooler and its plumbing, which don't get drained when the oil is
changed.

He said I would have noticed this before if I had ever checked it two hours
after a change. Since I check the oil before every flight, it seems I would
have noticed the oil's turning black this soon before.

Should I pay to have the cylinders 'scoped?

Dan,

I have a Lyc IO360 and the oil definitely does not turn black after two
hours. At two hours, it is still so light that I have trouble reading the
dipstick!

And I also have an oil cooler that does not get drained during the oil
change.

Aeroshell 15W50


--ron

How fast does it burn oil? My engine had fine compression but the valve
hardware was worn out. The oil got black real quick. Let me guess.....
there was a period of inactivity? Do you foul plugs? When was the last
overhaul? In my case, the overhaul was 17 years old. It finally hiccuped
in cruise flight. I had it overhauled.

"Dan Luke" wrote in message
...

wrote:

Definitely have an A&P borescope that engine. Broken ring maybe.

Talked to my mechanic this morning. He said not to worry; the dirty oil
is from the oil cooler and its plumbing, which don't get drained when the
oil is changed.

He said I would have noticed this before if I had ever checked it two
hours after a change. Since I check the oil before every flight, it seems
I would have noticed the oil's turning black this soon before.

Should I pay to have the cylinders 'scoped?

--
Dan
C-172RG at BFM