How much is to much?

[Flyin Tony]

How much oil burn is to much on a O540? Im using about 1qt for every 2 hours of flying.

 

[avbug]

Far from enough information is provided. If you're filling it (the engine) completely and counting the top quart or two, then you should expect to see it getting blown out regularly, and probably quickly.

Is the engine burning it or blowing it overboard?

Oil consumption of it's own accord doesn't mean a lot.

Are you fouling plugs? Do you have good compression? Have you seen a significant change in fuel burn? Any other problems? Is the engine smoking? Do you have a particular problem cylinder? A seal or prop problem? Where is your oil going?

 

[Wrenchnfly]

Lycoming publishes a service instruction 1427B that has a formula for max. oil consumption for all Lycoming engines. It is available on their website. I also agree to be sure that you are not filling to capacity. Most engines "blow out" the first quart or two out the breather. In an 8 quart sump I run 6 quarts as min. and anything under 6 gets a quart. 12 quart sump I shoot for about 10 quarts. 6 quarts go for 5. Anything under these "mins" and I add a quart. Usally this keeps them from blowing oil.

 

[Flyin Tony]

I keep the oil at 9qts, compression was all 75/80. When we bought the plane it was 72/80 on all of them. It only flew 10 hours in 3 years. It sat in a hangar at FUL for 31 years if that helps any. and about 700-800 SMOH

 

[USMCmech]

How many hours have you flown it since you bought it?


Sitting still for 3 years (or even 1 month) is the worst thing you can possibly do for an engine.

 

[avbug]

Many owners mistakenly believe that an engine should only be overhauled for hours. Let it sit for 30 years and it flies ten hours off of a 1,600 hour TBO...it still ought to have 1,590 hours until recommended overhaul, right?

Wrong. It should be overhauled immediately, if not scrapped. Sitting is death on engines and airplanes. As USMCMech said, it's the worst possible thing you can do short of setting the airplane on fire.

If the airplane didn't fly for 31 years, then it shouldn't have flown until being overhauled right off the bat.

Don't get caught up in compression readings meaning much of anything. Compression tests are generally meaningful to those who don't know better, and salesmen. Otherwise, unless every test was performed at the same temperature, using the same mechanic, using the same compressor and test set...too many variables exist to make the reading anything but significant by passing interest only.

Each time you do a compression test, the compression may go up or down, and that doesn't really mean a thing. Finding out why it did might...but don't assume that an engine with high compression is a good engine, any more than one that doesn't test well is a bad engine. It's just not the case.

Think in terms of age and time as well as hours. An engine that doesn't fly for three or four months should still undergo an oil change; acids are still washing into the oil, the oil can still be contaminated, and damage can still occur. An engine should be run regularly. You should be doing regular spectrometric oil analysis with every oil change, and the less you fly, the more you should consider changing the oil. Sitting idle kills mechanical things, especially airplane things.

Getting back to my previous question...where is the oil going? Blowing out the breather? Are you finding it on the belly? When uncowling the engine, is it wet? Are you finding fouled spark plugs to be a problem? Dark brown deposits showing up inside the lips of your exhaust stacks? You keep putting it in the engine, but you need to find out where it's going. For every bit the reason that you wouldn't do brain surgery merely because someone has a headache, looking at a teardown merely because you are losing some oil may be a bit premature. Let's find out where that oil is going, first.

 

[Flyin Tony]

I have 300 or so hours in it for a year and 4 months. It had a overhauled 1983 and has flown 900 hours (from the logs). I do know there is some comming out of the oil/air separator. Also there is some on the belly. We had a bore scope done and the mx man didnt seem to say there was too much to worry about. No plugs are fouling.

Dark brown deposits showing up inside the lips of your exhaust stacks

I will check that out tomorrow. What could that mean?

 

[USMCmech]

I have 300 or so hours in it for a year and 4 months. It had a overhauled 1983 and has flown 900 hours (from the logs).

That's a lot of sitting around for an engine. I personally suspect anything less than 100 hrs per year.


If the inside of the exaust has black soot, that indicates that you are burning the oil. The spark plugs will also collect black soot as well.

 

[avbug]

Black deposits can be oil but are more commonly attributed to an imcomplete fuel burn. Brown deposits are generally oil. White deposits are lead. A lot of folks cleaning their airplane don't realize this; those white deposits are highly toxic, and if you get it in your bloodstream (very possible when using liquid solvents and cleaners to remove it from your aircraft belly or exhaust), it can stay in you for a long time.

That it's coming out your breather and air oil separator indicate you may be putting too much oil in your engine. If you only keep it a quart below topped, perhaps you should try running it two quarts down for ten or twenty hours. If you find that your consumption suddenly drops, you have your answer.

From your description, which is very general, the appearance of topping too much oil appears to be the culprit. I'll add the disclaimer that to say with any certainty could only be done by examining the airplane in person. If you find that you are able to cut your consumption by using a lower oil level in general practice, don't assume that other things may not also be to blame...you may have other problems, and should never assume that the engine has only one issue. There may be more.

 

[TDTURBO]

How much oil burn is to much on a O540? Im using about 1qt for every 2 hours of flying.

I have an O-540 J3C5D, I can only give you the advice i received at numerous owner maintanance seminars given at our type club.


Which kind of plane is it, the breather tube may be a 1/4 inch to long extending out into the propwash therefore sucking oil out of the case.

Fix: Cut it flush with the point it exists the airframe and put a wistler slot in the center of it just in case the tube gets iced up and you don't blow the case, the biggest mistake I see you commiting is putting 9 quarts in this engine. It runs best on 6-6.5 max, you'll keep the belly much cleaner too.


This tactic has worked for 1500 hrs in my plane with no jugs coming off and one firewall forward G&N overhaul several years ago, after 2500 hrs of trouble free operation using 100+.

I have never had even a hiccup in 22 years of flying this engine.

P.M. me if you want to know other little known secrets regarding this motor, I like it because it won't ice up as well as a thousand other reasons,

It's also critical you lean the hell out of it when taxiing or you run the risk of fouling plugs.