Continental O-200 oil burn?

[Merritt]

Does anyone know whether Continental specify a 'maximum' allowable oil consumption on the O-200 engines? If so, please can you point me in the direction of the paperwork (I can't find anything useful on their web site)

Our continental O-200 is using around 1L/ph of oil in moderate cruise, which concerns me. The oil pressure is also very low (just in the green).

Any advice appreciated,

Thanks

Steve

[Engineer_aus]

Perhaps you need to take it to your engineer and have it looked at. 1L per hour I think off memory is still in limits, but its getting up there. I have known 200's to be using 2L per hour. Sounds like one of your bearings is gone.

[helifixer]

Holy crap brother! How can you afford internet whilst working on piston engine ****e.

[Merritt]

Thanks Engineer Aus,

The A/C is group owned (and im not the owner). I have reported it & the owner is looking for a replacement engine but he tells me it has been checked & is safe. Me being the paranoid type (and an Engineer albeit of the semiconductor electronics variety!) thought I'd do some research of my own.

If anyone comes across a halflife or replacement O-200 in the UK on their travels, please let me know!

Cheers

Steve

[Yoth]

I'd be tempted to giveit a good ground run and pull the oil filter. Split the filter and give it a thorough inspection for metal.
As a previous post says, sounds like a bearing has gone, or on it's way out.

[EchoMike]

O-200 oil burn and leaks

I'd look at some other things before blaming "a bearing".

First - "normal" oil consumption on an O-200 is about a liter every 15 hours or so, some a bit more, some a bit less.

Second - if you fill it to six quarts, "full" on the dipstick, the first hour or so will see half a quart (half a liter) go out the breather tube. You aren't burning it, it is now on the belly of the airplane. Generally, don't fill the oil tank on an O-200 to much past five quarts unless you are going for a six hour ride or more. Try setting the oil level to five quarts on the dipstick and recheck your hourly oil consumption then.

Third - O-200s leak oil, sometimes quite a bit. Check the valve covers (the edges will look like potato chips), check the oil sump gasket (there are two), check the front crank seal (oil appears on the back of the prop) AND check that the vacuum pump isn't bad - gaskets good and the correct gasket (vac pump replaced recently??), no leaks at the case-to-pump junction either. You'll very likely wind up straightening the edges of the valve covers, don't get Continental's valve cover gaskest, get a set of R.E.A.L. (trade name) silicone gaskets instead - about $20.

Oil pressure is OK if it is "in the green" - anywhere between 10 and 50 psi if the engine is above idle. On higher time engines, you may drop below the green at idle. I don't like seeing this, but it's there.

How many hours since MAJOR and how many hours since top overhaul? The bottom end is ready for an overhaul about every two tops - 3,500 hours and it is time for a bottom end overhaul ($$$$$$$$).

O-200s usually eat the center main bearing. You can buy +.010 bearings easily, you can get +.020 bearings under an STC but this gets expensive. Crank life is about 4,000 hours and then it is usually too worn to be reground.

Do you have oil on any/all of the spark plugs? If not, you aren't burning oil, it is leaking. If you have oil on ONE plug or both plugs in ONE jug, look there for your problem - cracked piston or broken rings, bad valve guide.

If a rod bearing is "going" it will sling oil on the cylinder bore and the oil ring won't be able to cope with it. You can change the con-rod bearings on an O-200 without splitting the case, and that's an easy palliative (not cure) for low oil presure.

If this is in an older Cessna 150, be aware that if the later spinner is fitted (the smaller, correct one is NLA), it partially covers the two oval air intakes in the bottom cowl - these guide air to the oil tank. If the motor mounts are also a little saggy (and they usually are) the two air intakes may be completely blocked, and the engine will run progressively hotter and hotter. This problem usually shows up in the summer time (like now) because the high ambient air temps plus the blocked air intakes are just too much. You don't hear too many complaints like this in the winter.

The cure is either no spinner or the beanie cap spinner and replace the eight rubber pucks which are the motor mounts (about $150).

You can check for a bad bearing by removing the cowl and using a long screwdriver as a stethoscope - be careful of the propeller!!! - listen around the center of the crankcase - a clunk-clunk-clunk sound at idle means it is overhaul time.

Do the cheap, easy stuff first before you go looking for another engine.

PM me if you want more info ;-)

Best Regards,

Echo Mike

[SNS3Guppy]

First of all, internal problems involving bearings and other metal surfaces will be found in an oil spectrometric analysis. Second, a spun bearing won't cause an oil increase in oil consumption. Third, nothing was said by the original poster to suggest a spun bearing. Fourth, not enough information is given. Fifth, we don't know the oil level the original poster is attempting to maintain when he keeps adding a liter. Sixth...oil pressure can easily be adjusted up.

Find the problem first, start small and simple, and work up from there. If you have doubts about the airplane, obviously don't fly it.

[Von Klinkerhoffen]

Seventh....when was the aircraft oil pressure gauge last check calibrated , it may be telling you porky's !! Eighth......what oil are you running , is it too thin for summer use ?

VK

[SNS3Guppy]

Good point(s)!

[NutLoose]

Agreed, first thing to check is the oil very dirty or black?

Have you had a compression check done of late?, it could be something really simple like glazed barrels or pushing it past the rings if they have lined up......

This might help for the above.



http://www.tcmlink.com/pdf2/SB03-3.pdf

[SNS3Guppy]

Oil color won't tell you anything about engine condition. Continental does say a rapid change within the first 10 hours of operation, but the truth is that oil may instantly discolor, and this means nothing. Without performing spectrometric oil analysis for a baseline, then making a trend comparison, smelling oil, looking at the oil, and feeling the oil won't really tell you anything.

The notion of piston ring gaps lining up to drop compression or increase oil consumption is an old one, but has no basis in fact.

[NutLoose]

Oil colour will tell you if its blowing past the rings or the barrels are glazed and rings lining up do cause a drop in pressure

[SNS3Guppy]

No, oil color really won't. The color of the oil may be due to a number of factors, but one can't tell the condition of the engine by the color of the oil.

This is one myth that most mechanics understand, but it's tough sometimes to convince the lay person. Engine oil color means nothing. If anything, it indicates that the oil is properly suspending material (ashless dispersant)...but even that's far too simplistic. If you want to know about the oil, looking at the color won't tell you anything useful. A spectrometric oil analysis done on a regular basis and compared against a baseline for trend analysis, will.

Quaker State Home

Motor Oil Myths and Facts

Oil Color Lubrication Ability and Contamination Level

Color of Engine Oil

Oil Myths and Facts

Whitfield Oil Company: Motor Oil Myths & Facts

The notion of staggering piston ring gaps has never had any substantiation, and most understand it to be an old wives tale. Never the less, the myth lives on. There is no difference in a compression test if the ring gaps are aligned, or staggered. Think about it.

When a leakage occurs in a cylinder, it doesn't happen necessarily around an "aligned" portion of the engine. It's a gas...it doesn't need to leak in a straight line, or because of alignment. There's nothing about lining up the gaps in piston rings that will make leakage occur at any greater rate than if they're staggered. Further, leakage around ring end gap is a non-issue, and is irrelevant to the performance of compression tests.

http://www.triplesdownunder.com/Inte...ing%20gaps.doc

[Cessna Pilot]

Super Guppy - it appears as though your links relate to automotive engines and oils, as opposed to piston aircraft engines. Aircraft engines are a little bit different from a car or truck. The color of engine oil is certainly an indicator of engine condition - if it turns black very soon after oil change blowby is likely very high. I'd be somewhat concerned about this engine - I had an engine with almost identical symptoms cause me to make a forced landing immediately after takeoff last year - thankfully no damage. Ironically, we had completed the annual inspection about 30 hours prior, and compressions were all better than 65/80. Oil pressure was low - it would get up to the bottom of the green when cold, but would hover around redline at idle. Technically it met the Type Certificate Data Sheet but barely (by the way, max oil consumption can be found in this document, available free at FAA: Home) Turns out our failure was from broken rings in one cylinder, and a bearing was starting to spin in the case! I suspect it is likely a valve was starting to stick as well, but we weren't able to confirm it for sure. Fortunately in my case, we were able to tear down the engine before we permanently damaged the crankcase and crankshaft. Was it expensive for the owner - oh yes!, but cheaper than trashing the whole engine. Disclaimer - my advice is worth what you paid for it - get a good mechanic and do a thorough checkup on this engine! Good luck and happy flying! CFI, A&P, and other alphabet soup

[NutLoose]

Totally agree with you Cessna Pilot, but after 35 years in the business, I just don't bite these days, when peeps try to tell me otherwise

[Malcom]

Oil colour will tell you if its blowing past the rings or the barrels are glazed and rings lining up do cause a drop in pressure

and if the valve guides are worn too.

and if the oil has been changed recently.

and if the engines done more hours than alleged in between changes.

[Big Pistons Forever]

Merrit

I have a copy of the Continental Motors A&C series & O200 Operators Manual (Form X30012) It states that the quote approx maximum desirable Oil Consumption : 0.6 Quarts per hour unquote(chart on page 4). Based on that it would appear that at 1Lt per hour your engine is exceeding the maximum consumption Continental specifies in their official document. I highly recommend your group acquire this publicatio as it has complete power curves and much more engine information than the Cessna POH

My experience has been that any of your typical small 4/6cylinder engines that used more than about a litre per 3 hours has had major problems. There is no way I would personally fly an airplane where the engine used this much oil.

[A and C]

Merritt

Would the oil be leaking so much that the owner puts the nose leg in a tray to keep the oil off the hangar floor?

If so I would suspect crankcase fretting.

[NutLoose]

I went to a Shell / Lycoming seminar and was told the way they determine the oil capacity of the sump is to work out the worst possible oil burn for the aircraft endurance then bung a couple more quarts in on top of that, that determines the size of the sump.

[SNS3Guppy]

- it appears as though your links relate to automotive engines and oils, as opposed to piston aircraft engines.

No, they really don't. They refer to statements made by the oil producers, among others, regarding oil color and analysis based on color...and it's equally applicable to aircraft or automotive applciations. I'm referring to air cooled reciprocating aircraft engines using formulated aircraft engine oils. The color of engine oil, however, is not a reliable indication in either recip aircraft engines, or automotive engines.

The color of engine oil is certainly an indicator of engine condition -

No, it really isn't. This is a myth. Every oil manufacturer specifically states as much as do each of the engine manufacturers. After more than a few years working on aircraft, I agree. If you want to know what's in that oil, a spectrometric oil analysis is the only way to go. Color tells you nothing. I've seen oil turn black right off the bat, and I've seen oil that scarcely changes color until the next oil change; color means nothing.

Don't take my word for it, though...

The Answer Book - Shell Aviation

Why does oil turn black between oil changes, and why does the time it takes to change colour vary?

When a straight mineral oil turns dark or black, it usually means that the oil is starting to oxidize and needs to be changed. Because mineral oil doesn’t absorb much of the dirt and sludge in your engine, the oil stays clean and the inside of your engine gets dirty. Ashless dispersant oils, on the other hand, are designed to get dirty so that the engine will stay clean. Just how quickly the oil turns black depends on a number of factors, including the condition of the engine, the dirt load, the oil temperature, the normal air/fuel mixture, the type of fuel, the time since the last service, and the frequency and duration of your flights. Basically, the important thing to remember is to change your ashless dispersant oil on calendar and engine time, not according to its color. Also, oil analysis can help ensure that the oil is still in good condition even though it may have turned black.

http://www.exxonmobil.com/lubes/exxo...1_OilColor.pdf

[QUOTE]The color of the oil will change during normal engine operation when additives do their job of protecting the base stock. Such changes do not affect the performance of the oil and do not indicate contamination or other malfunction.

The phenomenon referred to as “Black Oil” is not due to oil discoloration but to the suspension of very small amorphous particles in the oil. When the particles are filtered from the oil,the color reverts to normal. Black oil arises in certain engines due to an artifact of the engine design. It cannot be eliminated by oil development or reformation.

Motor Oil Myths and Facts

The Dark Oil Myth
Dark oil does not indicate the need for an oil change. The way modern detergent motor oil works is that minute particles of soot are suspended in the oil. These minute particles pose no danger to your engine, but they cause the oil to darken. A non-detergent oil would stay clearer than a detergent oil because all the soot would be left on the internal engine parts and would create sludge. If you never changed your oil, eventually the oil would no longer be able to suspend any more particles in the oil and sludge would form. Fortunately, by following the manufacturer's recommended oil change interval, you are changing your oil long before the oil has become saturated. Remember, a good oil should get dirty as it does it's work cleaning out the engine. The dispersant should stop all the gunk from depositing in the oil pan.

The only real way to determine whether oil is truly in need of changing is to have an oil analysis performed. Since most people don't want to bother with this, it's acceptable to err heavily on the safe side and simply follow the manufacturer's recommended change interval for severe service. There are still a few cars that specify 3K intervals for severe service, but not many. If you look at countries other than the U.S., the oil recommended change interval is much higher than even the normal interval specified by vehicle manufacturers in the U.S.

Color of oil isn't a reliable method of determining engine health in automotive or aircraft engines. If anything should be noted with respect to color, it's not the actual color one sees, but two independent factors worth noting in some cases (but not all): rate of color change, and transparency of an oil sample film. It's not uncommon for a rapid change of oil color to occur, and this is not a reliable indication of engine health, but may be a clue to do further investigating...especially if historically this has not occurred with this particular engine. So far as light and oil color of a film sample, this is still subjective and requires spectrometric analysis for any meaningful insight.

This thread primarily concerns oil consumption, not color. Oil consumption is a product of many factors, but the actual rate of consumption is a trifle compared to changes in the rate of consumption. Whether the engine is burning a liter an hour or two or none, it's much more important to look at the history of the engine and note changes.

Is the original poster filling the engine to capacity every time...and subsequently seeing a liter or two blown out the breather? Most piston engines prefer to run a quart or two low, and any extra will quickly be blown overboard. This doesn't indicate an engine health issue, but an operator error issue.

I went to a Shell / Lycoming seminar and was told the way they determine the oil capacity of the sump is to work out the worst possible oil burn for the aircraft endurance then bung a couple more quarts in on top of that, that determines the size of the sump.

That's the method? See how much it needs and "bung a couple more quarts in on top?" It's a little more exacting than that. The certification standards for recip piston engines, to include engines such as the 0-200, are that the sump holds double what the engine actually requires. It's found in the certification regulation 14 CFR 33.39 (Airworthiness Standards, Aircraft Engines), and reads:

§ 33.39 Lubrication system.

(a) The lubrication system of the engine must be designed and constructed so that it will function properly in all flight attitudes and atmospheric conditions in which the airplane is expected to operate. In wet sump engines, this requirement must be met when only one-half of the maximum lubricant supply is in the engine.

Typical maximum oil consumption for a small piston engine is about a quart an hour...which equates to just over a liter. This isn't necessarily a bad thing. If there are concerns, one should be performing inspections and maintenance to determine if further investigation or work is warranted.

Oil consumption increases as oil degrades. Longer times between oil change intervals may see an increase in consumption in some engines.

Teledyne Continental makes the following statement about oil consumption:

Teledyne Continental Motors ||Visitor Services||

Evaluate the overall oil consumption with respect to the engine installation. In general, look for stability of oil consumption rather than level as a health indicator. If you have a highly loaded installation or turbocharged engine, you may want to evaluate and reflect on the oil consumption rate between a multi-viscosity oil and a straight-weight oil. Generally the use of multi viscosity oil will result in a lower oil consumption level. It is not harmful to change the basic type of oil used in the engine and to evaluate the result.

And, of course...

To guide the long-term oil selection and engine monitoring process, I would begin a disciplined oil analysis program. Again, our TCMLINK Aviator Services program provides a convenient and cost effective method for the owner/operator to track his oil analysis results. Followed with discipline, oil analysis can help you monitor engine wear trends somewhat more scientifically as compared to reliance on "hangar talk".

So far as "hangar talk," what you won't find from Shell or Mobil, or Continental or Lycoming...is a reference suggesting you should determine your engine's health using oil color. You'll find a number of references to spectrometric oil analysis, however...which is a little more scientific and accurate than guessing about the engine because you think you know something about the color.

You'll also find that the emphasis isn't on the amount of oil the engine is burning or passing, but on the stability of that rate of consumption. If you're one liter an hour now but it changes to two on the next flight, you may have a problem. Likewise, if it suddenly drops, you may have a problem, such as an occluded breather with an impending shaft seal failure...something along those lines. Change in the rate of consumption is much more important than how much is actually being consumed or lost.

Continental provides the maximum consumption number based on the percentage of power at which the engine has been operating, as .006 X %power, divided by 100. The result is the lbs per brake horsepower per hour, max. You can view the document at: http://www.tcmlink.com/EngSpecSheetDocs/O200A.doc

Technically it met the Type Certificate Data Sheet but barely (by the way, max oil consumption can be found in this document, available free at FAA: Home)

As far as the TCDS and legal official max oil consumption, re: the TCDS...do you happen to see it there?

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/8f38ff75fb7ad83d8625763500632b82/$FILE/E-252.pdf

No?

...and rings lining up do cause a drop in pressure

A ridiculously outdated myth that wasn't true when people still believed it. It wasn't true long ago, and is not true now, despite the fact that some still cling to this false notion.