We have a multipoint EGT monitor & we use it to lean in cruise. I know the rings occasionally stick as we have had one leaking by at annual a time or 2 (different cylinders) we follow Continental's guidance & fly it & recheck, it is OK when we recheck. We try to do the compression check at annual with the engine hot if possible.
I know we are well within limits on oil usage, my reason for posting was that this is a change, & some people have expressed some concern. I was looking for some guidance from people with more experience with aircraft engines, as all my experience is with water cooled automotive or tractor engines.
So it is good that you are paying attention to oil consumption. And I will note that the Continental "acceptable" level of oil usage means very little when looking at an individual engine. Each engine has its own consumption pattern following its break in. So the very reasonable question is why your oil usage has gone up.
A big clue is that you have a history with this engine, probably across only the last few annual inspections, of observing some sticky rings. We know that these sorts of issues rarely cure themselves. We watch them develop and when they get to the point that we decide that the situation has moved from a concern to a problem, we spend money and take action. In your case, my guess is that if you are not seeing oil on the outside of the engine, you should look for it on the belly. Are your club members complaining about a greasy belly? Or more to the point, if you do not normally look there, is your belly more oily than previously?
If the annual is several months away and you are concerned enough to spend a couple of $$, a compression check might be informative.
The other thing I would ask is how hard you are leaning and what power settings do you and your peers typically run? What CHT's? And may we assume that you are flying a Cessna product?
And we have neglected to ask - what brand and weight of oil are you using?
Best of luck,
Wes
Once 4 or 5 years ago, then again Dec 2011 at annual
Not that I can tell, but it doesn't get cleaned as often as I would like. I spend enough time taking care of the maintenance, I figure someone else can wash it.
Cessna 182, Phillips 20W50 & 1 pint camguard at oil change. How it gets flown depends on who is flying it, but most of us that fly it much fly at 2450 rpm, at an altitude high enough that the manifold pressure is in the green with the throttle all the way in. The CHT is the original Cessna gauge, we lean by the EGTs, run the hottest ones in the 1300 degree range & it gets us to the area of 13 - 13.5 gal per hour. Why they didn't spend a couple hundred more for the unit that also shows individual CHT readings I will never understand.
13 gallons per hour is not particularly lean for an O-470 in a C-182.
Too bad that you don't see the CHT's. A lot of older 182's have ragged baffle seals and can run warmer CHT's due to the reduced air flow through the cylinders. We also see vernatherms that do not seal well to force the oil to flow through the oil cooler rather than bypassing it.
In any case, if indeed you are getting more blow by the rings, the multi-grade oil is thinner base stock and so may allow more flow out the breather than a 100W oil. So since it is summer, you might try straight 100W AD oil of your favorite producer and see if the oil consumption goes down. Relatively inexpensive to try and you will get another data point to chew on.
Best of luck,
Wes
13 gal per hour was my normal fuel consumption in my T-34A with Cont 0-470-13.That is at about 9500 feet, full throttle, 2300 rpm and leaned. I didn't try to do lean of peak. Mine used a quart of oil every few hours.
Where is your oil going? Look in the exhaust, is it black or oily, or is it going out the breather or leaking onto the belly?
I don't know much about a "stuck" ring, and think that is unlikely in an engine that is broken in and using multi grade oil. I don't think Phillips would agree that 20-50 is going to consume much, if any, more than plain 50 wt. And if you haven't switched oils, that would not account for an increase. More likely, if anything, might be a broken oil control ring. If so , I would think you would see oily black residue on that bottom spark plug and not the other cylinders.
if you find low compression, listen to see where the leak is, exhaust, intake or breather.
To check rings, you might try squirting a little light engine oil in the top spark plug hole and rechecking. This won't change if valves are at fault, but give better compression if it seals the rings temporarily. This is easier to do in an upright cylinder than in a flat engine.
Last edited by Bill Greenwood; 07-21-2013 at 01:43 PM.
While not familiar with this particular engine, I'd suggest (as Wes suggested) running a compression test which is better described as a 'cylinder leakage test' and see where the leakeage (if any) is going. Otherwise it's just dancing around the issue. Kind of like going to the doctors office and they take your vital signs. If it's leaking past the rings and into the crankcase it gives you some indication of wear. Having said that, I'm not a big fan of the compression (or cylinder leakage test) as there can be a lot of other factors that will influence a temporary compression leak. In other words: use the test for 'information' but don't condemn it on the basis of one test. One needs to remember that the piston is in the TDC position for only a 'millisecond' when the engine is running, plus the compression rings get part of their sealing ability from combustion pressures pushing getting behind the rings and pushing the rings tight against the cylinder walls.......80 psi is hardly able to duplicate that conditiion. The rest of the ring pressure comes from a large 'free diameter' which increases ring tension. If this tension is lost by overheating or carbon building up in the grooves, gas pressure can escape and wind up in the crankcase. Oil that gets dirty early is an indication of that. Finally a compression test will not show broken or stuck oil rings. The oil consumption that you're describing does seem a little excessive but I'd run it for awhile and see what happens while keeping my eye on the 'vital signs'.
Good luck, Mike
If God had intended man to fly He would have given us more money!