Oil Consumption - O320

[avmg]

Maybe the forum can help.. I have a Ram STC'd O320 rated for 160 HP. It consumes a quart of Aeroshell 15w50 every seven to ten hours, would this be considered a normal amount? I am also operating an O320 that is unmodified, and it consumes a quart every 25 hours or so. It doesn't need to have oil added between 50 hour inspections. One other thing: I fill both airplanes to 6 quarts maximum. Thank you..

[black hole]

Yes

BH

[2R]

http://www.lycoming.com/support/tips-ad ... index.html

Enjoy

[avmg]

That link was helpful, thanks! Have a good one..

[Hedley]

I would be more concerned about the engine that
only burns a quart every 25 hours

[iflyforpie]

I would be more concerned about the engine that
only burns a quart every 25 hours

Why is that? My on condition IO-520 (2100hrs) only went through a quart every 25 and my factory IO-520 does less than that. Am I missing something?

P.S. 1 qt per 10 hours is perfectly normal and healthy.

[Hedley]

1 qt per 10 hours is perfectly normal and healthy

It surely is. Heck, I can toss a quart out the crankcase breather
(by overflowing the Christen 601 inverted oil system slobber pot)
simply by doing 0.1 on the tach worth of unlimited aerobatics
over the runway. Again, perfectly acceptable, according to
Lycoming.

Anyways. I thought that fad had passed - where people said
that an engine which burned a quart of oil every 20 hours was
twice as good as an engine which burned a quart of oil every
10 hours, and that an engine which burned a quart of oil every
40 hours was twice as good an engine as the one that burns
a quart every 20 hours.

Hogwash.

It doesn't hurt to let the oil scraper ring pass a little crankcase
oil up. A friend of mine just ferried a Spad - a Douglas A-1 Skyraider -
across the North Atlantic from Europe, and it had lots of external
gas, and was actually limited in range by oil consumption, which
was measured in gallons per hour for that huge radial engine. They
didn't have time to rig up a wobble pump from a 55 gal drum.

The engine wasn't worn out - it was purposely and carefully rebuilt
that way, to allow the oil to get up, and to reduce wear.

Anyways. Obscure and irrelevant trivia, soon to be lost in
the mists of time.

[ThatGuyYouKnow]

AVMG,

A quart every 7 to 10 hours is acceptable, even less time than that would probably still be okay. How many hours are on your engine? A new engine will most likely have higher than normal oil consumption due to the oil ring not worked in yet, and of course a higher time engine because of the wear issues. A quart every 25 hours is amazing. I have never seen an engine making it that long without toping up the oil. Six quarts is okay, anything more and you'll probably just blow it out the breather.

[avmg]

That's great, thanks for all the feedback! The "consumer" has about 500 hrs. on it, and it "feels" much smoother than the other engine. It's good to know that a guy can learn something useful in these forums, thanks.

[Hedley]

How do you know when the rings are worn unacceptably?

There is a rule of thumb that says that if the compression
is less than 60 over 80, you need to tear the cylinder down -
either an exhaust valve in serious trouble, or a broken/worn
ring, which actually isn't that big a deal.

Lycoming has a formula for calculating acceptable oil burn,
it comes out to something incredible like 0.7 quarts per hour.

Continental has a weird setup where you measure the
crankcase pressure (?) with some meter, to measure
blowby. Neat idea. Never seen (or heard) of anyone
doing it, ever.

Here's how you know if your rings are too badly worn:

A little oil on the bottom plug is ok - but it's a sign that
your rings are wearing - but when you have oil on the
top plug, it's time to pull the jug and change the rings.

Just looking at the spark plugs will tell you an awful lot
about your engine.

[iflyforpie]

Continental has a weird setup where you measure the
crankcase pressure (?) with some meter, to measure
blowby. Neat idea. Never seen (or heard) of anyone
doing it, ever.

The only thing I do different with a Continental is use the 0.040 calibrated orifice that is either built into the newer compression testers or fits onto the spark plug adapter. Whatever your second gauge reads with pressure set to 80psi, that's what you are allowed to go down to. Most days it sits around the 40~50/80 mark .

The low figures don't seem to affect power output too much, and I've had a few times where leak downs were back up to more respectable levels on the next check.

[c170b53]

Mine may burn a quart in 25 hours of operation, the interval of my oil changes (chrome cylinders)( 20w-50xc). Check the plugs is a good tip. Compression check will tell where the loss of pressure is, not why, of course. I pulled a cylinder because it was 20 lbs low, leaking at the exhaust valve. The first annual a tap at the valve was the cure, the second annual I thought something must be up to have the same valve with the same problem. Nope just my steady bad luck, cleaned the valve seat, reinstalled the cylinder and without renewing any parts oil consumption has remained the same.

[ThatGuyYouKnow]

Couldn't agree with you more Hedley. Spark plug inspection is a great way to understand what your engine is doing. Too rich, too lean, ring condition, and of course the plug itself to check gap and electrode condition.
Cheers.