Minimum Oil Level

Sure, and Lycoming also says that an engine can burn up to around 1 quart of oil every 4 hours, and still be airworthy (0.006 lbs. / HP / Hr). Of course you would never want to get anywhere near that. These are maximum/minimum limits - not recommendations.
 
I knew my O-320-D3G minimum oil quantity was 2 qts, but it wasn't listed in the Limitations section of the POH. I KNEW it was in there somewhere. Searched on "minimum" and found it in Section 8.19 - AIRPLANE HANDLING, SERVICING AND MAINTENANCE/OIL REQUIREMENTS
"The oil capacity of engine is 8 quarts, and the minimum safe quantity is 2 quarts."

Frankly 2 quarts doesn't sound "safe" to me.
 
If you combine both limitations, you could fly with only 2 qts in the sump while the engine burns 1 qt every 4 hours, which means as soon as you take off, the engine won't have enough oil.
 
MRC01 said:
Sure, and Lycoming also says that an engine can burn up to around 1 quart of oil every 4 hours, and still be airworthy (0.006 lbs. / HP / Hr). Of course you would never want to get anywhere near that. These are maximum/minimum limits - not recommendations.
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Thinking is expected of the pilot.

Or, at least it was when these things were written. Now we have a couple of generations of pilots spoiled by modern cars that require one to push the button to start it, then you point it where you want to go and press Go or Stop. Very little maintenance required, almost no oil consumption at all, so it gets driven until it finally quits and the driver gets to wait for help. This sort of thing never did work in aviation, and still doesn't.
 
Domenick said:
Frankly 2 quarts doesn't sound "safe" to me.
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Here we have a thinking pilot. I wouldn't consider it safe either, especially if the engine was tired and used lots of oil, or if the oil cooler hoses were old and could start leaking at any time, or if the engine tended to run hot at that level.
 
MRC01 said:
If you combine both limitations, you could fly with only 2 qts in the sump while the engine burns 1 qt every 4 hours, which means as soon as you take off, the engine won't have enough oil.
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Yup.

But any Lyc/Cont opposed engine that burns that much oil needs an overhaul. That's over 12 quarts in 50 hours.
 
Dan Thomas said:
But any Lyc/Cont opposed engine that burns that much oil needs an overhaul. That's over 12 quarts in 50 hours.
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Not necessarily. That much oil consumption can be caused by a stuck oil ring, which can often be cleared by a solvent flush.

The O-290 in my Hatz was burning more that that... but compressions were good and the plugs were clean. It was annoying, but not a safety of flight issue, and O-290s are known to consume oil even when not overfilled. I planned to do a solvent flush this spring, but sold the plane (with full disclosure) before I got around to it.
 
Dan Thomas said:
But any Lyc/Cont opposed engine that burns that much oil (0.25 qt / hour) needs an overhaul. That's over 12 quarts in 50 hours.
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Dana said:
Not necessarily. That much oil consumption can be caused by a stuck oil ring, which can often be cleared by a solvent flush.
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True. The point is there is something wrong with the engine that needs attention - whether or not it is an overhaul.
 
Garee said:
I don’t think anyone is suggesting you fly around with 2 quarts of oil, but when you land and discover you only have 2 quarts left, is that you don’t have to worry if your engine was damaged…….
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Agreed, that is how I interpret the Lycoming guidance.
 
Keep in mind that some of that oil lost may not be being burned or spit out the breather tube. It could be coming from a bad crankshaft seal.
 
The engine doesn’t know or care how much oil is in the sump it just knows if it’s sucking oil or air. The benifit to having more is less chance it’s gonna suck air if you get the plane steep and the more oil the longer the oil stays clean simply because there’s more oil to catch the carbon etc. but having too much isn’t good either. If it’s hitting the crank that’s trying to spin it can affect fuel consumption to a degree as it’s just adding friction having to get shoved out of the way. I know a guy who builds small block chevys and races them and he told me he only ran 3 quarts bc any more would slow it down a fraction on the 1/4 mile. So just know filling it to the brim isn’t all roses. Your engine might thank you if you give it a little elbow room inside. Just change it often. It definitely will love you for that.
 
Nova said:
The engine doesn’t know or care how much oil is in the sump it just knows if it’s sucking oil or air. The benifit to having more is less chance it’s gonna suck air if you get the plane steep and the more oil the longer the oil stays clean simply because there’s more oil to catch the carbon etc. but having too much isn’t good either. If it’s hitting the crank that’s trying to spin it can affect fuel consumption to a degree as it’s just adding friction having to get shoved out of the way. I know a guy who builds small block chevys and races them and he told me he only ran 3 quarts bc any more would slow it down a fraction on the 1/4 mile. So just know filling it to the brim isn’t all roses. Your engine might thank you if you give it a little elbow room inside. Just change it often. It definitely will love you for that.
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He should also use light weight oil, no 10w40 for racing.

Also use minimum oil in the transmission.

NASCAR has been doing this for decades.
 
Cars don't pitch and reports of what works or doesn't work in them are slightly interesting and irrelevant.

Read manuals and limitations for minimal oil levels as a function of attitude. Below that, you are sucking air at the pickup.
 
Nova said:
So just know filling it to the brim isn’t all roses.
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All kidding aside, I do agree with Nova on this. To add, accidentally overfilling can be bad, leading to frothing / aeration and loss of lubrication.

Net net, keep as much oil in the engine between the Add line and just below the Fill line as the engine will retain without tossing it out the breather, and you should be good. I think I mentioned before that my 0 470 Continental will toss out everything beyond 9 quarts. Some engines just have a quirk that there's a level they like.
 
Always wanted a air oil separator. On mooney would’ve been tight. Do they work?
 
bonefishpete said:
Always wanted a air oil separator. On mooney would’ve been tight. Do they work?
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Sometimes. Don't think they are still available new for certificated aircraft. Usually only see them on aircraft that at one time did the Airwolf separator STC (no longer available), or older aircraft still fitted with a wet vacuum pump. In the latter case they seem to work ok.

Won't solve excessive oil use because of excessive crankcase pressure (there's a Continental test for that, unsure for Lycoming), though may neaten things slightly.
 
My 0-320 likes 6 qts and when it get's to 5 qts I add one.
The other day when it was about 20°F I added a qt. Took a while to drain out of the bottle even though it was 15W50.
Today is the last cold day for a while around here. Tomorrow it's going to be much nicer out. Too bad our airport is going to be closed from 7am tomorrow through 5 PM Thurs afternoon for 3-4 weeks!
I have been flying the last 3 days in the cold to get some hours in.
 
bonefishpete said:
Always wanted a air oil separator. On mooney would’ve been tight. Do they work?
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Those separators filter the oil out of the crankcase breather exhaust, but they also filter out the water in that exhaust, and they return both the oil and water to the crankcase, making corrosion a much bigger problem. We had one on one of the flight school 172s, and it didn't even filter out the oil all that well. There was still oil on the belly. Worse, the Instructions for Continued Airworthiness for that STC demands that the separator be removed and opened and cleaned every 100 hours or so. That's a pile of really dirty work.
 
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