Van's Air Force
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Oil Burn in a 0-360 ?
- Thread starter blkfin
- Start date
gmcjetpilot
Well Known Member
Well he is honest
Lycoming does not publish an exact oil use except for break-in but guide lines. 4 hr/qt could be considered normal with caveats. Personally I like to see at least 8 hr/qt or better. Frankly my O360 was in the 16 hr/qt per hour range after 900 hours, but than I flew it 300 hours in 2 years not 10 years. The low hours bothers me the most.
Lycoming says an engine that gets 4 hrs/qt or 20 hrs/qt can both be healthy. There's other criteria to judge health. Compression, power and limits. Is oil temp & pressure OK? Is the oil filter free of debris? Last but not least is trend monitoring of oil use. If its always used oil 4 hr/qt it may be normal. It's also possible the rings never seated. Also any time oil use JUMPS more than a qt you may want start to investigate.
I would consider getting an AI to do the compression check for you independently and even bore-scope the cylinders and possibly look at the cam (some small dis assembly needed). If it cost a few $100 its worth it.
Oil use is a function how harder you run it and how much you fly. Engines run frequently are better and use less oil than ones infrequently flown. You can have bad rings, valve guides that allow more oil use. Seal leaks can be an issue as well.
A Lyc will run fine using oil if the plugs are not fouled and all limits are in the green. However I would not like 4 hr/qt personally. It would bug me. Here are some PDF's of Lycoming Key Reprints, where they discuss oil consumption and "what does it mean?" Look in General, Maintenance and Operations. Good info in there. What ever you pay plan on a top end or about $4,000-$5,000 in the price. Now compare to an ALL brand new 360 for about $21,000. Don't pay too much. A complete overhaul may be in the $10,000-$14,000 range or more. If you pay $10,000 and find you need an overhaul, it may cost you a lot more than just buying new. Plus you get a warranty with a new engine.
http://www.lycoming.textron.com/support/tips-advice/key-reprints/index.jsp
Here is just a few excerpts from Lycomings Key Reprints:
QUESTION: At what rate of oil consumption does continued operation of the engine become a hazard?
ANSWER: Generally speaking, when the oil consumption reaches one quart per hour, corrective action should be taken. However, maximum permissible for each particular engine is listed in the engine operator’s manual.
QUESTION: What are the dangers of operating an engine with high oil consumption?
ANSWER: When excessive amounts of oil get past the rings, there is danger of the ring sticking or breaking with a dramatic rise in oil consumption. Then oil soaked carbon forms at a fast rate. At the same time, the presence of oil in the combustion chamber has the effect of lowering the octane rating of the fuel. Operating temperatures go up. We have now set up conditions inviting detonation and/or preignition.
QUESTION: What are some common causes of excessive oil consumption other than the burning of oil due to high
engine time?
ANSWER: Building up of crankcase pressure due to “blow-by” caused by ring wear may result in oil being blown out of the breather. The same thing can result from broken piston rings. Oil may be pumped overboard due to a faulty vacuum pump or faulty automotive-type fuel pump.
At least he is being honest. Most people would lie, "Oil, it does not use any". To me 4 hr/qt sounds high for a 300 hour engine, but not necessarily non-normal. 300 hours in 10 years is low use, which is not great, corrosion wise. Those are my first impressions. Ask him how high he filled his oil level To! It's common knowledge and accepted practice to keep oil at or less than 6 qts. Most agree that any thing much over 6 qts gets blown out the engine. If he was in the practice of putting in 8 qts all the time his oil consumption may be the result of his practice of over filling the oil level, more than actual indication of engine condition.
Lycoming does not publish an exact oil use except for break-in but guide lines. 4 hr/qt could be considered normal with caveats. Personally I like to see at least 8 hr/qt or better. Frankly my O360 was in the 16 hr/qt per hour range after 900 hours, but than I flew it 300 hours in 2 years not 10 years. The low hours bothers me the most.
Lycoming says an engine that gets 4 hrs/qt or 20 hrs/qt can both be healthy. There's other criteria to judge health. Compression, power and limits. Is oil temp & pressure OK? Is the oil filter free of debris? Last but not least is trend monitoring of oil use. If its always used oil 4 hr/qt it may be normal. It's also possible the rings never seated. Also any time oil use JUMPS more than a qt you may want start to investigate.
I would consider getting an AI to do the compression check for you independently and even bore-scope the cylinders and possibly look at the cam (some small dis assembly needed). If it cost a few $100 its worth it.
Oil use is a function how harder you run it and how much you fly. Engines run frequently are better and use less oil than ones infrequently flown. You can have bad rings, valve guides that allow more oil use. Seal leaks can be an issue as well.
A Lyc will run fine using oil if the plugs are not fouled and all limits are in the green. However I would not like 4 hr/qt personally. It would bug me. Here are some PDF's of Lycoming Key Reprints, where they discuss oil consumption and "what does it mean?" Look in General, Maintenance and Operations. Good info in there. What ever you pay plan on a top end or about $4,000-$5,000 in the price. Now compare to an ALL brand new 360 for about $21,000. Don't pay too much. A complete overhaul may be in the $10,000-$14,000 range or more. If you pay $10,000 and find you need an overhaul, it may cost you a lot more than just buying new. Plus you get a warranty with a new engine.
http://www.lycoming.textron.com/support/tips-advice/key-reprints/index.jsp
Here is just a few excerpts from Lycomings Key Reprints:
QUESTION: At what rate of oil consumption does continued operation of the engine become a hazard?
ANSWER: Generally speaking, when the oil consumption reaches one quart per hour, corrective action should be taken. However, maximum permissible for each particular engine is listed in the engine operator’s manual.
QUESTION: What are the dangers of operating an engine with high oil consumption?
ANSWER: When excessive amounts of oil get past the rings, there is danger of the ring sticking or breaking with a dramatic rise in oil consumption. Then oil soaked carbon forms at a fast rate. At the same time, the presence of oil in the combustion chamber has the effect of lowering the octane rating of the fuel. Operating temperatures go up. We have now set up conditions inviting detonation and/or preignition.
QUESTION: What are some common causes of excessive oil consumption other than the burning of oil due to high
engine time?
ANSWER: Building up of crankcase pressure due to “blow-by” caused by ring wear may result in oil being blown out of the breather. The same thing can result from broken piston rings. Oil may be pumped overboard due to a faulty vacuum pump or faulty automotive-type fuel pump.
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If he is keeping it filled to 8qts it's not burning the oil. It's blowing out the breather.
If you do a compression check on each cyl and put a hose in your ear and the other end in (1) oil filler tube (2) Injection servo/carb (3) exhaust and they all sound similar and the compression readings are similar and the sparks plugs are not oil soaked....... then there is probably nothing wrong with the engine and if you ran it at 6 qts the burn rate(loss rate) would change.
Ask him how long it takes for the oil to get dark..... if he says fast like less than 10 hours that's not good...... perhaps worn cyl or broken ring.... in which case the offending jug might show (1) oily spark plugs (2) hissing sound out the oil filler tube as described above. Not the end of the world easy repair.
If you do a compression check on each cyl and put a hose in your ear and the other end in (1) oil filler tube (2) Injection servo/carb (3) exhaust and they all sound similar and the compression readings are similar and the sparks plugs are not oil soaked....... then there is probably nothing wrong with the engine and if you ran it at 6 qts the burn rate(loss rate) would change.
Ask him how long it takes for the oil to get dark..... if he says fast like less than 10 hours that's not good...... perhaps worn cyl or broken ring.... in which case the offending jug might show (1) oily spark plugs (2) hissing sound out the oil filler tube as described above. Not the end of the world easy repair.
gmcjetpilot
Well Known Member
Who knows
If you have to start replacing jugs you should replace all of them. Often when you put one new one bad things happen in short order to the other ones. Just my opinion and experience.
Who knows what he filled it up to, it was just a guess on my part.
If you have to start replacing jugs you should replace all of them. Often when you put one new one bad things happen in short order to the other ones. Just my opinion and experience.
zilik
VAF Moderator
You know, I fill mine to 8 qts at every oil change and I don't believe I have ever had any oil puke out the breather. To me this is a myth. Now if someone would step up and explain why the engine would blow blow, oil I am all ears.
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Oil blowing myth
The story I heard/read somewhere is that the FAA required engines to be able to run successfully on a small percentage of their oil capacity. Don't remember the percentage, but let's say it was 25%.
So if the engine makers determined that an engine needed 2 qts to run successfully, they filled the sumps up as full as they could get them, in this hypothetical case, 8 qts. This became the certificated "full" mark on the stick. If not for the certification requirements, the full mark would have been lower, say around 6.5 to 7 qts.
In a wet sump engine, if the oil level is too high, the crank and rods splash the oil as they spin, and even cause the oil to foam, which allows it to get blown out of the breather. Once the oil gets below the level at which it gets foamed up by the crank, no more foam, and no more oil blowing out.
This scenario is not true for dry-sump engines, such as the Pratt-Whitney R-1340 and many others, because the oil is in a remote tank, and can't get "foamed" by the crank.
OTOH, this just might be another one of them pesky urban legends!
The story I heard/read somewhere is that the FAA required engines to be able to run successfully on a small percentage of their oil capacity. Don't remember the percentage, but let's say it was 25%.
So if the engine makers determined that an engine needed 2 qts to run successfully, they filled the sumps up as full as they could get them, in this hypothetical case, 8 qts. This became the certificated "full" mark on the stick. If not for the certification requirements, the full mark would have been lower, say around 6.5 to 7 qts.
In a wet sump engine, if the oil level is too high, the crank and rods splash the oil as they spin, and even cause the oil to foam, which allows it to get blown out of the breather. Once the oil gets below the level at which it gets foamed up by the crank, no more foam, and no more oil blowing out.
This scenario is not true for dry-sump engines, such as the Pratt-Whitney R-1340 and many others, because the oil is in a remote tank, and can't get "foamed" by the crank.
OTOH, this just might be another one of them pesky urban legends!
The reason this happens is that the amount of oil inside the engine actually changes the crankcase pressure by varying the size of the inside of the engine. If you look at the total volume of space inside the engine, by changing the oil level you increase or decrease that volume of space by adding or removing oil. Adding a quart of oil would decrease the volume of space inside the engine by an amount equivalent to the volume of oil added. With a given supply of air pressure inside the engine(blow-by air from the cylinders) and a given outlet hole (breather fitting) varying the size of the inside of the engine, will vary the resultant crankcase air pressure. The higher the crankcase air pressure, the more tendency, we have to push oil vapors out the breather before the oil can separate from those vapors, resulting in the messy belly and oil usage. Once we get to a internal size or internal volume that is compatible with the blow-by and or breather size the internal crankcase pressure drops to a level that will allow the oil to separate from the vapors before being expelled from the engine, and the belly is cleaner and the usage stabilizes. Anything we do that effects this situation can effect the amount of oil we breath out. Restricting the breather outlet will increase the pressure and cause more oil breathing than a less restricted breather. Worn or unseated piston rings will cause more blow-by and the increase in pressure that goes with it, thus it will cause more breathing of oil out of the engine and like we discussed making the inside of the engine smaller will also increase the pressure making the engine breath the oil saturated vapors overboard. Some perfectly good running engines have less blow-by than others or a less restricted breather outlet than others and that is why some want to run two quarts low before they stop pushing the oil out the breather and others want to run only a 1/2 quart low for the same results. Likewise when there is something wrong with the engine that effects this combination we will breath the oil laded vapors out no matter what we do to try and stop it.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
pierre smith
Well Known Member
You're close
Pete, you're close. The FAA requirement is for the sump to hold twice the minimum oil. For my 180 Lyc it's 8 quarts and Lyc's min is 4 qts. I run 6 and don't add 'til it's below 5. Yes...it foams more than 6 out.
Pete, you're close. The FAA requirement is for the sump to hold twice the minimum oil. For my 180 Lyc it's 8 quarts and Lyc's min is 4 qts. I run 6 and don't add 'til it's below 5. Yes...it foams more than 6 out.
I keep mine at 6 qts
If I put 8 qts in my 0-360 I get a rapid reduction to 6 quarts in under 10 hours. It is all most likely coming out of the breather as the belly gets plenty messy. When it gets down to 6 quarts it stays there until my next oil change and the belly is much cleaner. I actually now only put in 7 quarts at oil change and then add the 8th quart at around 18 hours to keep it above the 6 quart line on the stick. I call that "no oil consumption" as I only use 8 quarts total for the oil change cycle.
If I put 8 qts in my 0-360 I get a rapid reduction to 6 quarts in under 10 hours. It is all most likely coming out of the breather as the belly gets plenty messy. When it gets down to 6 quarts it stays there until my next oil change and the belly is much cleaner. I actually now only put in 7 quarts at oil change and then add the 8th quart at around 18 hours to keep it above the 6 quart line on the stick. I call that "no oil consumption" as I only use 8 quarts total for the oil change cycle.
PC Hunt is close, as mentioned.
The FAA requires engine and airframe makers to design the engine oil capacity to be big enough so that if the engine is burning oil at the maximum allowable rate approved by the engine maker, that the airplane will run out of fuel before it runs out of oil.
So if the airplane has a 5 hour fuel endurance, and the engine is considered healthy with 1 hour per quart burn, then you need 5 quarts more capacity in the sump than the minimum it needs to run.
So most sumps are much bigger than necessary, and with all the splashing and frothing going on in there when the sump is full it ends up going out the breather.
If you have a good seperator it will minimize this to a great extent.
The FAA requires engine and airframe makers to design the engine oil capacity to be big enough so that if the engine is burning oil at the maximum allowable rate approved by the engine maker, that the airplane will run out of fuel before it runs out of oil.
So if the airplane has a 5 hour fuel endurance, and the engine is considered healthy with 1 hour per quart burn, then you need 5 quarts more capacity in the sump than the minimum it needs to run.
So most sumps are much bigger than necessary, and with all the splashing and frothing going on in there when the sump is full it ends up going out the breather.
If you have a good seperator it will minimize this to a great extent.
zilik
VAF Moderator
Mahlon had the best reasoning but still don't buy it. If the engine has a lot of blow-by then there is something else wrong. I really don't think volume of the crankcase will effect pressure change with a constant size exit opening.
The comment about the crank and rods splashing around in the oil would only happen if you put more than 8 quarts in the sump. The sump, sitting on a work bench holds just at 8 quarts and the crank is spinning above it with a crankcase separating the crank housing from the oil sump.
The comment about the crank and rods splashing around in the oil would only happen if you put more than 8 quarts in the sump. The sump, sitting on a work bench holds just at 8 quarts and the crank is spinning above it with a crankcase separating the crank housing from the oil sump.
zilik
VAF Moderator
What!
2 quarts in the first ten then stays at 6 for the remainder of the oil change. So during the last 15 to 40 hours (depending on 25 or 50 hour interval) the engine consumes none. 15 hours, zero oil consumption. I believe that.
Second scenario: Seven quarts at oil change, 1 quart 18 hours later to keep it above 6 quarts so I must assume it dropped to 5 or 5.5 quarts or you would not have added oil. So thats 1.5 to 2 quarts used in 18 hours yet you say "no oil consumption". Hmm. Must be new math.
My engine uses the first quart more slowly than the second. I dump 8 in at oil change and about 10 hours later I have to put another quart in as the stick is on 7. At 20 hours I'm sitting at 5.75 on the stick but don't usually bother to add oil since the oil change is only 5 hours away. Probably use another .5 to .75 quarts in the last 5 hours. So that gives me a consumption total of 2.5-2.75 quarts in 25 hours. Old math.
So as you can see, when we're hangar flying and talking about oil consumption we're comparing apples to oranges.
2 quarts in the first ten then stays at 6 for the remainder of the oil change. So during the last 15 to 40 hours (depending on 25 or 50 hour interval) the engine consumes none. 15 hours, zero oil consumption. I believe that.
Second scenario: Seven quarts at oil change, 1 quart 18 hours later to keep it above 6 quarts so I must assume it dropped to 5 or 5.5 quarts or you would not have added oil. So thats 1.5 to 2 quarts used in 18 hours yet you say "no oil consumption". Hmm. Must be new math.
My engine uses the first quart more slowly than the second. I dump 8 in at oil change and about 10 hours later I have to put another quart in as the stick is on 7. At 20 hours I'm sitting at 5.75 on the stick but don't usually bother to add oil since the oil change is only 5 hours away. Probably use another .5 to .75 quarts in the last 5 hours. So that gives me a consumption total of 2.5-2.75 quarts in 25 hours. Old math.
So as you can see, when we're hangar flying and talking about oil consumption we're comparing apples to oranges.
