How often are you adding oil?

[201er]

Since getting my Mooney M20J and the annual, I have flown about 10 hours. Oil was at 6 quarts starting out and was down to about 4.3 quarts when I added a quart to it. I was trying to hold off for just another hour because I'll be stopping by the mechanic and thought I'd do it then, but I was getting lower oil pressure (bottom of green arc) so I added a quart then. Comes out to about a quart for every 6 hours of operation. Does that sound about right to you?

How often are you adding oil? How far do you let it go down before you add more?

[jetdriven]

We fill at 5 and add one quart to make 6.  For a really long flight, fill to maybe 6.5 quarts.   Regardless, we don't let it get below 5.

[Piloto]

Your consumption rate of 1qt/6hours is in the ball park number. I found the consumption rate to increase with higher RPM. Running at 2400rpm or less you can get 1qt/8hours while at 2500rpm I get 1qt/6hours. It also varies with the age of the oil, new oil will last longer than 50 hours oil. I add oil when below 6qts. However for trips over 5 hours I fill to 8 qts. I have the M20 Oil Separator that keeps from discharging the top 8qt and keeps the belly clear of oil.

José    

[danb35]

Like Jose, I add when my level drops below 6 qt.  I fill with 7 when I change the oil and usually run 10-15 hours before I add 1, but after that it's more frequent.

[Shadrach]

Typically add at 5qts never really let it get to 5.  Were you in cruise with "Low oil pressure" came about. What was the oil temp? An IO360 will run fine on 4qts of oil. Your drop in pressure was likely related to the oil being hotter(which indirectly is related to quantity) than you're used to. 

[Ned Gravel]

I add one quart at 5 qts too.  Lasts anywhere from 6 to 7 hours that way.  Change it every 25 hours.

[201er]

Sounds like the oil practically replaces itself between oil changes and then oil change too! So that's about 10 quarts every 25 hours!?

[Shadrach]

I should have been more clear. When I change the oil. I fill to 7qts, this will show about 6.5 on the dipstick after the engine is run and the new filter fills up. Moving forward from there, I add whenever it drops below 5.5qts and try to avoid going as low as five. I do 30 hr oil changes between which I've added as little as 1qt or as much as 2qts depending on the type of flying I'm doing and the OAT. It uses a qt every 12 to 15hrs on average, a little more in the hot summer months... I just did my first oil change on an IRAN'd engine (cracked crankcase) at 11.2hrs and I needed to add no oil during that period, even with all of the spillage that came with having the prop off twice... but thats another story! 

[jlunseth]

Well, I don't have a J so can't speak to J oil use, but 6 hrs. per qt. just seems too high to me.  Knowing what I know now, I just wouldn't accept that.

When I first got my K usage seemed to be about 10 hrs. per qt. but at some point last summer when I had gotten my IFR, I was taking longer trips and climbing at 100% BHP to altitude.  This was just after an annual.  I had oil on the belly after those climbs, but read alot about how turbos will do that when you climb at 100% so thought it was normal, although I didn't like it.  I was going through about 1 qt. per 6 hrs. if a long trip, 1 qt. in 10 hours for local flights where I did not make the climb.

We then had a flight where, to keep it short, we found that a piece of plastic had entered the quick drain and we were blowing oil out the quick drain.  Had that fixed, and also had the valve cover gaskets replaced cause they were leaking.  I also replaced the #1 (hottest) cylinder at annual because of low compression. 

With that done and the same engine, a bad day is 1 qt. per 10 hours, and more often I will go through an entire oil change adding 1 qt. - and I go 40-50 hours between changes because of frequent flying.

I have a mid time (1000 hrs.) turbo.  I can do a 100% climb to FL240 now and not lose a drop.

Most of the oil was going out that quick drain.

[jetdriven]

Lycoming has a formula and for the IO-360 and its ,64 QT/HR before something must be done.   6-10 hours per quart is fine.  Oil isnt that expensive. If you are using 1 quart in 50 hours start budgeting for a top overhaul, because the rings arent passing enough oil.  You are going to wear the tiop of the bore out.  Airplane engines are purposely set up loose, because they are air cooled and they have a large temperature range to operate in.  2500 RPM cruise will use more oil.  Also, oil on the bely isnt burned oil, its blown out so don't count that.

[jelswick]

I've always tried to keep mine about 7 and add a qt when it gets down close to 6.  It does seem to blow that out down to 6, pretty quickly, so I'm adding about every 4 hrs of use.  I saw a number of you don't add until down to 5-5.5.  I've never let it get that low thinking I needed to keep it between 6-7.  I'm assuming with the number of you using that range, I'm keeping to much in my J and paying to just blow it out back to 6 where it seems to like to be.

[N601RX]

We were using about 1.2 quarts per hour.  When we pulled the cylinder the oil ring fell out in several pieces.

[Jeff_S]

My experience matches most of the others here. We put in 7 quarts at the change, and I can usually get 10+ hours before it gets down to under the 6qt mark on the dipstick. I can tell when this has happened because the oil pressure gauge settles right at the bottom of the green in cruise. After that, I usually get about 5 hours before adding another quart, and I just keep that up until the change.

I will say that I switched from AeroShell 15W-50 to Phillips 20W-50 about a year ago, and started using AvBlend, all at the advice of Jerry Manthey during one of his last clinics. I don't have solid, long-term empirical data to support the following statement, but it does seem like my oil use has dropped a bit, the oil seems to stay "cleaner" longer, and my Blackstone Labs oil analyses just keep getting better.

[201er]

My mechanic told me that the engine can run fine down to just a few quarts of oil so you have a good safety margin on the low end. But putting in anything over 6 is pointless cause it just gets blown back out. His advice was fill to 6, drop to 5, return to 6. The only reason I was letting it go further was to see how much it's dropping and to show my mech when I get to him. But when it got below 4.5 and I saw oil pressure a bit lower I decided not to wait any more.

[Shadrach]

201er,

Your oil pressure likely dropped because your oil temp has higher. It works like this..

Less oil lubing the same amount of engine has to carry more heat.

Hotter oil will have a lower viscosity.

A system pumping lower viscosity oil will show will show lower pressure...

[201er]

Very interesting. So how low below 6 is ok to go? What's the lowest anyone here has gone? What is your bare minimum (say you're oil is low, you have none with you, gotta fly to your mech for oil change, what's the least oil you'll go on)?

[Shadrach]

Check the TCDS for your engine type (faa.gov) I believe it gives the minimum oil amount needed for constant operations. I personally always keep it above 5.5qts unless I know I'll be changing the oil in the next few hours.

Also, at least in my case, I have anecdotal evidence that my plane burns more oil at higher oil temps. In the winter, even with the cooler "winterized" it will rarely exceed 180. In the summer I see 210-215. My airplane uses more oil at the higher temps. YMMV...

[jetdriven]

The IO-360-A TCDS lists the minimum safe oil quantity as 2 Qts.  We put in 5 at the last change and ran it a few minutes and it wouldnt show on the dipstick.

[bd32322]

i am in the fill to 6 - wait till it drops to 5 camp. anything over about 6.5 gets thrown out. I bought mine recently - so dont have historical data but after about 34 hours I went through 3.5 quarts. I am using aeroshell 100w plus. sae 50 oil. Engine is at 1750 hours although cylinders were changed at 1000 hours by previous owner.

[David Mazer]

My Rocket was taking about 1 qt/4 hr until last year when I had some interior work down in Venice FL.  When it came back it took 2qt/hr for a few hours and then settled back to about 1 qt/2 hr.  Needless to say, the engine was rebuilt and in the about 100hrs of flying since then, I have not added 1 qt of oil except at oil changes (10 hrs for the first and 30 hrs increments after that). I have been adding CamGaurd at each oil change now.  I should have added it before I let the guys in Venice let my plane sit for a couple months.  Lesson learned.  Or, should I say, expensive lesson learned.

[The-sky-captain]

The "Venice Guys"... uuggghhhhhh!!

[David Mazer]

So you know of them, do you?  I have taken to wearing this T shirt at SNF to express my opinion of their work.

[The-sky-captain]

Mazerbase- That shirt is awesome! You could probably make a ton of $ selling that baby at Mooney gatherings:)

Yeah, I had a dealing with him when I purchased my plane. Long story short it was a terrible experience.Many other Mooneyspace users have had issues as well. Love the shirt, kep rocking it!

[David Mazer]

Ah, but if I had only known to check his reputation at MooneySpace before I let him touch my plane.  Mia culpa though since I must have not done due diligence sufficient to uncover what appears to be one of the worst kept secrets in the Mooney world - stay away from them.