Lycoming oil capacity question aeio-320 ???

Hey folks I have searched and searched for some info on this engine. recently bought a Decathlon with a 150horse constant speed prop. On the dipstick it of course reccomends 8 qrts just like the manual, The engine has 600 smoh, good compressions (mid 70's), and runs great. I can add a quart to get it up to 6qrts on the dipstick and fly it for 2 or so hrs and it will be down to 5 qrts, I was wondering if it is blowing some out, and actually holding more than it says on the stick with the inverted oil system(wondering if a quart or two of oil is trapped in the oil system when it sets and doesn't drain into the oil pan). The engine has no leaks or anything, doesn't seem to be blowing out any. just wondering if anyone has any thoughts. sorry for the blabbering but I guess you get the jist of my question. I

What happens at 5 quarts?

What is the minimum? Two quarts?

Personally, if it stays level at five quarts I would probably make that INDICATED level the norm.

Hey Ron, I think its going to stay level at 4 qrts indicated on the dipstick,, and if the christen system will hold two or so in the lines and inverted tank I guess it is fine, but if the christen system drains in to oilpan after shutdown then I guess there is something going on, but I don't know if the christen inverted system will drain or if it just sort of holds the oil in the lines and inverted tank????? looking at the lines I would guess it would atleast hold 2 qrts in the system. thx for any info.

Christen invert system

Manual says 2 quarts is minimum for engine. Christen system may change minimums.

I have heard from A&P that the auto ball valve gets stuck over time if not serviced/cleaned. It is suggested this may be part of your problem. Check logs to see when the last time this part was serviced. Worth looking into as it may need to be serviced anyway.

Thx nick I will have to look into that, I guess I will just let it run at 4 quarts on the stick and see if it stays steady there or not????

oil quantity

Hi, Sounds like the plane is a recent purchase, you didn't say how many times you have added the qt to bring it up to 6. I'm not too familiar with the inverted system but seems to me if you use a standard say always check the oil 10 min after shutdown, or whatever you choose, then you should be able to get a feel for what's happening. My O-360 was a fresh overhaul and used a qt about every 3 -4 hrs ran great and had good compression. fixed it with a good honing and a set of rings. If you have added the oil more than a few times, not throwing it out the breather or leaking, you either have some unknown storage or your burning it. If your burning the oil it may be only one or two cylinders and you might be able to tell by doing a careful spark plug inspection following a flight. A nice tan color on the plug is what you want and if one or two are darker or blackish carbon then that is likely the one. Lycoming says these engines will run on as little as two quarts, not sure if they say it's safe to run on that little but supposedly they will. I always run mine between 5.5 an 6.5.

Thanks for the info Jerry, Im going to drop the oil out of it tommorow, and put a fresh 8qrts in and see what happens from a baseline. keep up with the oil usage and hours for a bit..

Just for FYI guys, we took the compressions on the cylinders and number 2 cylinder only had 45psi, so that is the culprit to why I'm using oil and why the oil is blacker than normal.. It sounds like its hissing through the dipstick so it isn't a valve should be the piston/ring bore, cracked ring or something, gonna pull it this weekend.

Follow up

Thanks for following up with your oil consumption. Sorry about you cylinder news. Keep us posted on the repair. Good luck.

Will do Nick and thanks for the advice.

Expect to find a broken oil ring due to end gap clearance.......

I wish it would be that simple gasman, and would the broke oil ring cause the big compression loss???

Hey guys I know it has been a month since, but just as a final update, I sent the cylinder off to Gibson Aviation, and he said the rings were shot and had a cracked exhaust port, sent me a reman cylinder back with everything new except piston itself, currently have 6 hrs on the new cylinder, everything is lovely, and I was very impressed with Gibson Aviations customer service and willingness to answer all of my dumb questions.