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Minimum Oil level - IO-390

J

jimkwalton

Active Member
I was testing oil consumption vs oil level. After my last oil change, 7qts plus CamGuard showed 7.5 on the oil stick. I ran the engine 15 hours all the way down to 4 on the oil stick. On the last flight with the starting oil at 4 qts I experienced a rapid fluctuation in the oil pressure between 55-65 psi. Before my next flight I put 3 qts in back up to around 7.5 on the stick. Oil pressure back to normal. So, even though Lycoming says that all the way down to half capacity (8 qt system, 4 qt is half) is safe, my recommendation is not below 5 qts. I measured and graft the consumption over those 15 hours of flying and found no significant difference in oil usage (or blow-by) between 7.5 level and 4 on the dipstick. For this reason, and knowing that oil is a primary coolant for the engine, I will be keeping my oil above 6 from now on. The book also says that the engine circulates 8 qts per minute which I find to be a fairly low circulation rate but this is only a 4-cylinder engine, not a turboprop (the C-130 cycles the oil in the reservoir 30-60 times per minute depending upon oil level in the engine).
 
Never let the oil level get below 5 qts on a 390 (at least mine) and try not to go above 6 qts. For my 390 above 6 qts I lose about a qt every 6 hrs and below 6 qts about a qt every 9 hrs. 5 to 6 qts seems to be the sweat spot.
 
jimkwalton said:
The book also says that the engine circulates 8 qts per minute which I find to be a fairly low circulation rate but this is only a 4-cylinder engine...
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Which book Jim? I was told 7 gallons per minute for the standard pump and 9 for engines with a high capacity pump.
 
+1 on that. On my -14A with IO-390, I change oil and filter and add 6 quarts. After a short ground run it drops to about 5.3 on the dipstick overnight. I run it down to 5 and then add a quart. I'm always operating between 5 and slightly over 6 and normally get 10-12 hours per quart. Oil temp runs about 190 in cruise, varying between 165 on a super cold day and 205 on a hot one.

Bill Marvel
 
Jim, did you ever calibrate your dipstick? Mine was indicating a higher oil capacity than was really in the engine for low oil levels, but was accurate at the high end. There was a recall - - Lycoming wanted me to order a new one for $175 pay shipping then apply for warranty. Not the way I work - it was noted in the log book.
 
Minimum oil level is dependent on the sump style. The updraft sumps apparently tolerate a much lower level than the integral-style horizontal induction (not the EXP-119) sumps need. My own horiz sump starts sucking air bubbles at around 5 quarts. A quick test while flying is to do a forward slip to the right and then left (forgot which direction it's most sensitive to), but I can see the pressure drop a bit in the slip. Then I know it's time to add more oil. Yes, I check the dipstick on preflight, but the filter drains back a bit after a week and skews higher than what the actual level is.
 
A1AVIATON47 said:
Send out oil sample see if there is any metal in it, rapid fluctuation in the oil pressure does not sound good.
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Doesn't sound good, but rapidly fluctuations +/- 10 psi is exactly what a Lycoming engine does when it's at the lower end of the book allowable oil level..
 
BillL said:
Jim, did you ever calibrate your dipstick? Mine was indicating a higher oil capacity than was really in the engine for low oil levels, but was accurate at the high end. There was a recall - - Lycoming wanted me to order a new one for $175 pay shipping then apply for warranty. Not the way I work - it was noted in the log book.
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It's very easy to buy blank 6061-T6 aluminum rod to replace the dipstick level gauge rod. I have done this multiple times. The rod is attached to the cap with a roll pin looking thing (at least on the ones I have worked on). Once I figure a length of the new rod (I like to keep it 1/4" shorter than sump floor contact) I attach it to the screw-in cap. Starting with an empty sump and the aircraft in it's parked attitude (note tailwheel vs tri-gear will indicate differently) I start to add one quart at a time an make a small scribe on the dipstick rod for each level. For a professional looking job I then take a tubing cutter and very lightly run it around the rod diameter at each scribe location to make a perfect mark around the rod. Then I use number punches to add the quart quantity at each mark. Custom and very accurate for your particular aircraft. Better than the pricey Lycoming factory marked rod.
 
jliltd said:
It's very easy to buy blank 6061-T6 aluminum rod to replace the dipstick level gauge rod. I have done this multiple times. The rod is attached to the cap with a roll pin looking thing (at least on the ones I have worked on). Once I figure a length of the new rod (I like to keep it 1/4" shorter than sump floor contact) I attach it to the screw-in cap. Starting with an empty sump and the aircraft in it's parked attitude (note tailwheel vs tri-gear will indicate differently) I start to add one quart at a time an make a small scribe on the dipstick rod for each level. For a professional looking job I then take a tubing cutter and very lightly run it around the rod diameter at each scribe location to make a perfect mark around the rod. Then I use number punches to add the quart quantity at each mark. Custom and very accurate for your particular aircraft. Better than the pricey Lycoming factory marked rod.
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You can also do a double scribe (2 rings) at your Minimum operating level. This allows you to see the safe level without rotating the dip stick around to read the stamped numbers.... Lift it straight up, read it and screw it back in.
 
gasman said:
You can also do a double scribe (2 rings) at your Minimum operating level. This allows you to see the safe level without rotating the dip stick around to read the stamped numbers.... Lift it straight up, read it and screw it back in.
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Warren, you clever dog...

Now where's my tubing cutter?

Back to topic, I've noticed a slight increase in oil temperature when I drop below 6 qts, but offhand I can't say just how far below. Never been less than 5. Typically I run between 6 and 7. No hard evidence, but I suspect the increase is due to less time for deaeration.

Should be no difference between the 360 angle valve and the 390 .
 
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I too noticed a +/- 10 PSI fluctuation in oil pressure in my -390 (not EXP) in my 14A when I encountered turbulence or inducing a yaw. Pressure never dropped out of the green, but it was unnerving to see the fluctuations. I had the pressure relief valve apart a number of times, but never saw anything amiss. I finally narrowed it down to oil level. As long as I have over six quarts showing on the dipstick, there’s no fluctuation. I’m happy to finally hear others have similar experiences because I couldn’t find any other mention of it.
 
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hgerhardt said:
Minimum oil level is dependent on the sump style. The updraft sumps apparently tolerate a much lower level than the integral-style horizontal induction (not the EXP-119) sumps need. My own horiz sump starts sucking air bubbles at around 5 quarts. A quick test while flying is to do a forward slip to the right and then left (forgot which direction it's most sensitive to), but I can see the pressure drop a bit in the slip. Then I know it's time to add more oil. Yes, I check the dipstick on preflight, but the filter drains back a bit after a week and skews higher than what the actual level is.
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A good preflight is to check the oil before you take off
 
DanH said:
Warren, you clever dog...

Now where's my tubing cutter?

Back to topic, I've noticed a slight increase in oil temperature when I drop below 6 qts, but offhand I can't say just how far below. Never been less than 5. Typically I run between 6 and 7. No hard evidence, but I suspect the increase is due to less time for deaeration.

Should be no difference between the 360 angle valve and the 390 .
Click to expand...
I actually just used a sharpie and made a ring at max and min. I wasn't too excited about cutting a scribe around something that could drop into the sump...... no harm, just a P.I.T.A. to retrieve if.
 
I actually calibrated my dipstick by adding 1 quart at a time. I have a -14 taildragger and wanted to know accurately how much oil I have in it when the plane is in the 3 point position. I also have experienced oil pressure fluctuations in turbulence when below 5 quarts, still well in the green but some fluctuations. My minimum is now 5.
 
Jetmart said:
I actually calibrated my dipstick by adding 1 quart at a time. I have a -14 taildragger and wanted to know accurately how much oil I have in it when the plane is in the 3 point position.
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After my engine was installed, all the storage oil was drained and the dipstick calibrated with break-in mineral oil one quart at a time. I was lucky, the marks Lycoming had on the stick were 100% accurate for my installation.

There is an old saying in aviation. Trust but verify. When that is done, there is a lot less to worry about when flying.
 
DanH said:
Which book Jim? I was told 7 gallons per minute for the standard pump and 9 for engines with a high capacity pump.
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You are correct on the flow rate: GALLONS/minute, not quarts. So approximately 3-4 total times the oil is cycled through the engine each minute. Thanks for the correction.
 
I have an IO-360 in the RV-4. The dipstick has two sets of markings, neither correct. I run six quarts and add at five. When I change oil and filter I put in 5 quarts, warm it up and put it away. The next morning I check the oil level, note the level and then add a quart and note that level. I think I will use the tubing cutter to mark the 5 quart mark next time.
 
swjohnsey said:
Minimum oil level from the Lycoming service manual for all O-360s is 2 quarts!
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Note that some IO-360's have a 4 quart minimum. See this page from the Operator's Manual:

i-PXKvCRk-XL.jpg
 
dmattmul said:
Never let the oil level get below 5 qts on a 390 (at least mine) and try not to go above 6 qts. For my 390 above 6 qts I lose about a qt every 6 hrs and below 6 qts about a qt every 9 hrs. 5 to 6 qts seems to be the sweat spot.
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Exactly the same on my 390, occasionally I'll get 10 Hrs. Not sure why it is this way, but it's always been a bit disappointing having experienced an 0-360 in a previous plane that pretty much made it between 35 Hr. oil changes without having to add any oil! Sure, lower compression, but such a big difference! Luckily the many reports on the forum of others having similar consumption on their 390s makes me feel a little better, or at least accept it without worrying too much if I messed up the break-in!
 
I recently bought a 2019 RV-14A with the 210 HP YIO390 with 325 TTE. While keeping the stick between 5-6 qts, it is burning a quart every 3.6 to 4 hours. :(
Many of the 20 hrs that I’ve flown in the past 2 weeks are practice instrument approaches with about 15 MAP for about 8 miles. Then 25x25 in the climb and 23x23 in the 10 mile cruise back to the IAF, then repeat 1/2 dozen times.
On a 3-1/2 hr flight this weekend at roughly 23x23, she seemed to burn closer to 5hrs per qt.

The 2nd owner died in his PA-46 in December. His widow does not know how much oil he was adding to his RV-14A.
The log shows it broke-in with Aeroshell 100 mineral oil for 10 hours, then switched to Phillips XC 20-50 until 250 hrs when it started running Aeroshell W-100. Last month, 305 TTE, compressions were 1) 78/80, 2) 78/80, 3) 78/80, 4) 77/80. FWIW, cyl 4 does go LOP dirst, but they all go LOP within .5 GPH.

My 2014 RV7 had an Aerosport Power O-375 with 100 hrs, that burned a quart every 4 hours until I had Lycon diamond hone the nikasil-plated bores and replace the pistons & rings. The builder had babied the engine since day-1. He also babied an RV-9 that he built and it used a lot of oil.
I broke in the new cross-hatches in with no warm-up, a short taxi, then firewalled her for the first hour, then varied between 75%-65% power for the 2nd hour, then kept the power in the 65%-95% range for another 8 hours. By the 10 hour mark, it was burning at a rate of 1QT every 10 hours, so I sold her with a clear conscience.

I had a 2007 RV-7A, and for the past 2 years (170 hrs) have had my 2019 RV8. Both of these RV’s had Superior IO360’s. They both use a quart about every 9-11 hours if I top them up to 6qts, and a lot quicker if I over-fill. When I had the crank replaced (under AD) last year, Lycon bored my eight .010” and installed 10.5:1 pistons, ported the heads and Aladyne-dipped the heads. I broke it in just like the Aerosport 0-375 in my RV7. I’m happy to report that with these mods and one Surefly mag, top sreed went from 181 KTAS to 190 KTAS. Oil consumption is 1 qt every 10 hours with 70 hours on the top end.

So, my question on the YIO390 is: considering that it has great compressions, will do 174 KTAS fire-walled (and leaned to about 12-13 GPH) at 4500 MSL, oil temps are maybe 170, and CHT’s are 330ish (lower than my Superior IO 360’s and a lot lower than the Aerosport Power O-375).
There is barely any residue on the belly in the 20 hours that I’ve flown it, and no wet black ash in the tailpipe, but it does drip pregnant drop of oil on the breather tip when I land.

Question: should I have the cyls honed and/or bored .010” over, (and look into higher comp pistons and porting), then break her in hard, or should I just “run it”?
 
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I'd just run it. My IO390 burns a quart every 4 hours too. I have 680 hours TTE and fly at least once a week. Compressions are all 78+ and samples are normal. I run W100 and Camguard. From what I can tell, everything is normal and the engine runs great. It just burns more oil than I'm used to on other Lycomings. I'd rather put oil in a bit more often than pull jugs.
 
Angle valve engines have a tendency to use oil during low power settings Such as taxiing or long waits for takeoff clearance. I wouldn‘t do a thing with the engine regarding that.
i would suggest you get the oil temps between 190 and 200.
 
Just run it. I have a 390 that was broken in correctly as far as I’m concerned and I get 7-8 hrs on a quart. 200 hrs on it. I have stopped worrying about it. Most reports are that 390’s burn more oil.
 
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