IO-550G... How much oil?

[flyingcheesehead]

Realistically, how much oil is enough in an IO-550-G? And I don't mean the "as long as you have two quarts out of eight you're good" that you get from some official engine documentation - That's what the manual for the Lyc IO-360 says but I prefer 6 out of 8 in that engine.

 

[Henning]

Realistically, how much oil is enough in an IO-550-G? And I don't mean the "as long as you have two quarts out of eight you're good" that you get from some official engine documentation - That's what the manual for the Lyc IO-360 says but I prefer 6 out of 8 in that engine.

Almost every wet sump airplane engine I've come across does best at 2-3 quarts below the top indicator on the stick as the 6 of 8 on your 360. My 470s are quite happy holding at 9 quarts for 7-9 hours after coming down from 10 to 9 in 2. If I fill to 12 I'm at 10 in an hour.

 

[Piloto]

I have the M20 Oil Separator http://www.m-20turbos.com/index.php on my IO-360. I fill to 8qts and it will take on the average 10 hours to drop to 7qts. The plane belly is completely clean with no oil residue. Easy to install but tricky. The separator inlet has to be above the engine breather outlet to be effective.

José

 

[kgruber]

SOme of the new Continental engines use very little oil. My IO-520D used 1 qt. per 25 hours. Kept it at 12 qts.

 

[gismo]

Realistically, how much oil is enough in an IO-550-G? And I don't mean the "as long as you have two quarts out of eight you're good" that you get from some official engine documentation - That's what the manual for the Lyc IO-360 says but I prefer 6 out of 8 in that engine.

Most engines are certified to run when half full of oil. Unless it has a dry sump, they usually need close to half capacity so that the pump inlet doesn't unport in a steep descent or climb. Of course you would want to have enough that the level will be higher than that at the end of a long flight so you should add more based on the consumption rate and the endurance of the airplane. As others have mentioned it's common for airplane engines to use more oil when the pan is full compared to running a quart or two below the maximum.

 

[NineThreeKilo]

Depends on what you are doing with it, with the location of the oil pump, if you are cranking and banking you will want at least 9qt else you will loose oil pressure in a steep turn, unless you G load the turn.

 

[flyingcheesehead]

Can't do 9 quarts, it only holds 8.

I ask because I'd normally like 6-6.5 on an 8-qt. system. This one goes down to 5.5 in a hurry, and then pretty much stays put right there. Compressions are excellent, so I don't think it's a crankcase pressurizing issue, but it bugs me that I can't hold my 6+.

 

[NineThreeKilo]

Can't do 9 quarts, it only holds 8.

I ask because I'd normally like 6-6.5 on an 8-qt. system. This one goes down to 5.5 in a hurry, and then pretty much stays put right there. Compressions are excellent, so I don't think it's a crankcase pressurizing issue, but it bugs me that I can't hold my 6+.

Must be a difference with the 550G, ours held 10qts

 

[Skylane81E]

From the TCDS on oil sump capacity in quarts...
8; 5 usable at 16° noseup and 4.5 usable at 10° nosedown attitude

 

[Capt. Geoffrey Thorpe]

Almost every wet sump airplane engine I've come across does best at 2-3 quarts below the top indicator on the stick.

Then you have never come across a Jabiru.

 

[denverpilot]

Can't do 9 quarts, it only holds 8.

I ask because I'd normally like 6-6.5 on an 8-qt. system. This one goes down to 5.5 in a hurry, and then pretty much stays put right there. Compressions are excellent, so I don't think it's a crankcase pressurizing issue, but it bugs me that I can't hold my 6+.

I hate it when I can't hold my oil, too.

 

[gismo]

Depends on what you are doing with it, with the location of the oil pump, if you are cranking and banking you will want at least 9qt else you will loose oil pressure in a steep turn, unless you G load the turn.

Huh? Baring a very steep climb or descent, if the plane is reasonably coordinated (i.e. not flying knife edge) and you maintain at least some positive g loading I doubt that any IO-550 would see the slightest decrease in oil pressure during a steep turn.

 

[NineThreeKilo]

Huh? Baring a very steep climb or descent, if the plane is reasonably coordinated (i.e. not flying knife edge) and you maintain at least some positive g loading I doubt that any IO-550 would see the slightest decrease in oil pressure during a steep turn.

And yet it does, normally bank well over 60, pitch 30-45 and sure enough we do get some hiccups on the oil pres if the oil level is below 9qts.

 

[BurtM]

And yet it does, normally bank well over 60, pitch 30-45 and sure enough we do get some hiccups on the oil pres if the oil level is below 9qts.

Are you flying a Zivko?

Just trying to understand what AC that has an IO-550 that experiences the conditions you mention.

I think the Zivko runs a Lyc IO-540...

 

[gismo]

And yet it does, normally bank well over 60, pitch 30-45 and sure enough we do get some hiccups on the oil pres if the oil level is below 9qts.

High pitch angles I can believe, but as long as you're coordinated a steep turn by itself should increase the amount of oil in the sump as the extra g force assists gravity in returning splashed oil.

 

[comanchepilot]

Enough?

 

[Henning]

Then you have never come across a Jabiru.

Never will either, I don't buy complex things made in Australia, never know if you got a "she be right mate" one or not... I lived and worked there long enough to learn that lesson.

 

[flyingcheesehead]

Enough?

I'm just still trying to figure out what constitutes "enough."

 

[gismo]

Can't do 9 quarts, it only holds 8.

I ask because I'd normally like 6-6.5 on an 8-qt. system. This one goes down to 5.5 in a hurry, and then pretty much stays put right there. Compressions are excellent, so I don't think it's a crankcase pressurizing issue, but it bugs me that I can't hold my 6+.

How confident are you about the accuracy of the dipstick?

 

[comanchepilot]

I have an IO-540-N1A5. Manual says the sump is full at 12. The manual tells me never to let it get less than 2. Like many - when I keep 9 quarts in, within 2-3 hours I am down to 8 and it stays at 8 literally forever.

So - why blow out all over the belly that I later have to clean off? I could spend $400 to install an air / oil sep but its not going to stop the blow off to 8 quarts - they never have.

Thus - when I change my oil I put 9 quarts in. I put the other 3 from the case into the airplane as my 'traveling oil' . . . After I start the engine and run up the leak check the dip shows about 8.5 and I'm good.

If you run your engine over where it will hold oil, then all you are going is putting oil on the belly you are going to have to clean off. If I only put in that 9 quarts - I'll go 15 hours before I need to add a quart. which means a case of oil lasts me 45 hours - and then its time for the oil change. Sure - I have a 45 hour reminder for the oil change in the 530 . . .but the oil burn is just as reliable. . ..

When I said 'enough,' as long as you have more oil than the recommended minimum you are 'ok' and when you find out what your maximum operating level is - thats 'enough.'

 

[flyingcheesehead]

How confident are you about the accuracy of the dipstick?

Well, I have absolutely nothing to base it off of yet. I'm hoping to find an A&P who will show me how to change the oil so that I can do it myself. If I do, then I can put in a quart at a time and have a good idea of how accurate the stick is.

Of course, all of this begs the question "why do airplanes blow oil overboard?" I know that we started blowing more overboard on the O-470 when the compression in one of the cylinders dropped quite a bit, allowing the crankcase to become slightly pressurized... That makes sense to me. But, that's not the case on this IO-550, the compressions are all high. What other things cause oil to be blown overboard?

 

[Henning]

It's all in the machinists art of fine tuning the dwell of the cylinder with the hone to match the CHT one tunes for in cruise. The more precisely you as the operator can tune your temp profile parameters, the closer tolerance the machine work can be done to. If too much crank windage ends up in the oil it creates a huge mist/froth that goes out the breather. Also our engines lack a PCV system which they really should have.

 

[chemgeek]

I fill my O-320 to 7 qt (holds 8) and add when it reaches 6 qt. I think the Lycoming manual says it can run indefinitely at normal power at 4 qt. Usually running 1-2 qt under capacity avoids needless blow off. My new engine doesn't do this, but the old one always threw off the first quart in an hour or two, then settled down to 8-10 hr/qt.

 

[gismo]

Well, I have absolutely nothing to base it off of yet. I'm hoping to find an A&P who will show me how to change the oil so that I can do it myself. If I do, then I can put in a quart at a time and have a good idea of how accurate the stick is.

Of course, all of this begs the question "why do airplanes blow oil overboard?" I know that we started blowing more overboard on the O-470 when the compression in one of the cylinders dropped quite a bit, allowing the crankcase to become slightly pressurized... That makes sense to me. But, that's not the case on this IO-550, the compressions are all high. What other things cause oil to be blown overboard?

Two things (together) cause oil to escape from the crankcase through the breather. One is that the moving parts in the crankcase can stir the oil up to the point of atomizing some of it making a fine oil mist the inside the case. The other is blowby which pressurizes the crankcase thereby driving some of the mist out the breather. All engines have some level of blowby but one with worn/leaky rings will have a lot more and AFaIK that's the main reason why worn compression rings (vs the oil control ring at the bottom of the piston) increase oil consumption. A leaking front crank oil seal will cause the same problem as excess blowby in flight when the high pressure air at the front of the engine pushes past the seal and increases the pressure inside the crankcase.

AFaIK, oil separators were originally implemented to extract the significant amount of oil in the exhaust stream of wet vacuum pumps but somewhere along the line it was found that by passing the crankcase breather air through a separator, much of the oil that would otherwise be dumped overboard could be returned to the sump along with the oil from the vacuum pump. Unfortunately it appears that in the case of high blowby, the oil separators available for aircraft become overwhelmed and fail to return a significant amount of breather oil.

BTW, changing the oil and filter yourself is dirt simple but different than doing the same thing to your car or truck. There are 3 differences: 1) The filter has a hex nut on the end and should be tightened with a torque wrench 2), The filter must be safety wired to something and 3) You should cut the filter open and examine the paper element for metal.

#3 is the only "complicated" part, both WRT to the cutting and the inspection. You could do the rest and then have a mechanic show you how to do the filter afterwards.

Dan Macdonald's book on owner maintenance would also be a good source for that kind of information:

http://www.aircraftmaint.com/

 

[flyingcheesehead]

AFaIK, oil separators were originally implemented to extract the significant amount of oil in the exhaust stream of wet vacuum pumps but somewhere along the line it was found that by passing the crankcase breather air through a separator, much of the oil that would otherwise be dumped overboard could be returned to the sump along with the oil from the vacuum pump. Unfortunately it appears that in the case of high blowby, the oil separators available for aircraft become overwhelmed and fail to return a significant amount of breather oil.

Interestingly enough, my uncle purchased an oil separator but never had it installed. Wish he were around so I could ask why! I found it amongst a bunch of his other airplane stuff. I've heard that some people recommend against them because they could mask other problems with the engine?

BTW, changing the oil and filter yourself is dirt simple but different than doing the same thing to your car or truck.

Yup - That's why I'd like another pair of eyes on it the first time.

Dan Macdonald's book on owner maintenance would also be a good source for that kind of information:

http://www.aircraftmaint.com/

Thanks for the link, I'll check that out.

 

[flyingron]

I keep my IO-550-B around 8-9 quarts. As with many engines, filling it up to 12 ends up spewing a lot of it out in short order. There's certification reasons why the sump has to hold that much.

 

[gismo]

Interestingly enough, my uncle purchased an oil separator but never had it installed. Wish he were around so I could ask why! I found it amongst a bunch of his other airplane stuff. I've heard that some people recommend against them because they could mask other problems with the engine?

AFaIK, the primary downside to oil separators is that they return a lot of corrosives and water to the oil sump along with the oil.

 

[Henning]

AFaIK, the primary downside to oil separators is that they return a lot of corrosives and water to the oil sump along with the oil.

The trick there is to mount the separator as close to the vent as possible so the corrosives and water don't have a chance to condense out to liquid before hitting to the out tube.

 

[Skylane81E]

They also can mask problems, had a Chiefain that still had "acceptable" oil usage without an intact ring in one engine.

 

[Henning]

They also can mask problems, had a Chiefain that still had "acceptable" oil usage without an intact ring in one engine.

Yeah, but I'll tell ya, a lot of that is because somebody is ignoring something being wrong long before failure. There are some very poor operators out there.