The Cessna 120-140 Association Forum

Hi,
I would like to know what is your recommandation for the min/max oil qty for a o-200 in a C140.

Cessna 150 data (same engine)
I was reading the C150 POH... 6 Quarts Max
o-200 OH Manual... 6 Quarts Max
Flight School where I'm located: 4 Quarts Min & 5 Quarts Max (otherwise it will spit some oil)

My guess is...
3 quarts min & 4 quarts max (the engine inclinaison)

Can you please let me know what are your recommendation

Thanks,
Mat

I don't have an answer for you, but, here's how the oil capacity is arrived at: it is twice the amount of oil required for adequate cooling through all phases of flight.

Irrespective of the fact that airframe (and cowl) design has a lot to do with cooling capability, the O-200 has a capacity of 6 quarts, so the absolute minimum you'd want to have would be 3. Depending on your consumption, you'd need some amount greater than 3 to take off with. Personally, I'd not want to land with less than 4 quarts on board.

Not sure what you meant by "the engine inclinaison".

As far as the difference between 5 quarts and 6, well, given the design of the oil system, I can't figure how it would make a hill of beans difference. The only explanation I've ever heard that makes the least bit of sense is if there is a leak in the fill cap gasket that allows the filler neck to be pressurized. This could interfere with oil draining back into the tank until the level in the tank drops below the point where the top of the fill neck intersects the tank.

Thanks for the info John.

I apologize for my french/english... "the engine inclinaison" is the engine tilt.

The C140 is a tailwheel.
I know it's 6 Qt in a C150 IAW the POH (same engine config) but the AC/engine is level on the ground due to the nose landing gear.
It's a little bit different from the C140 when we are checking the oil. I wasn't sure if the reading was accurate.

Previous owner was keeping the oil between 3 min & 4 max.
I'll follow your recommendation & go 4 min to 5 max.
I just want to avoid to overfill the engine.

BTW, I found a very small oil leak from my oil pressure gauge during the ferry flight. I don't like the installation & I don't believe it's OEM fitting (see attached picture).

I have an 0-200.

I keep it between 4.5 to 5.5 quarts of oil. I typically get about 10 hours per quart of oil. I let it get close to 4.5 quarts before I add any.

maverick_fa wrote: ↑Mon Oct 25, 2021 7:55 pm"the engine inclinaison" is the engine tilt.

Ah! The American spelling is inclination. Probably not the first word we'd choose, though.

The C140 is a tailwheel.

I knew that...

I know it's 6 Qt in a C150 IAW the POH (same engine config) but the AC/engine is level on the ground due to the nose landing gear.
It's a little bit different from the C140 when we are checking the oil. I wasn't sure if the reading was accurate.

Right, it doesn't affect the engine, but it does affect the accuracy of the dip stick. Best bet is to change the oil some day, and add 4 quarts and run the engine a bit and then see where it registers. Then add a quart and see where that comes to.

I just want to avoid to overfill the engine.

As long as the oil is completely contained in the tank it shouldn't matter to the engine.

BTW, I found a very small oil leak from my oil pressure gauge during the ferry flight. I don't like the installation & I don't believe it's OEM fitting (see attached picture).

The fittings look about right, but they also look as if they have been abused in the past. They are standard AN fittings, easy to replace. Use a little thread sealer on the pipe threads and it should be leak free. You can remake the copper flare if it looks suspect.

I also don't have a good answer for you. I've looked/asked around everywhere and can't find a textbook answer.

From my experience with my 0-200 3.5 qts is the lowest I will go (preferably only on a local flight). I did one short flight at 3 qts and my oil temp was much higher than normal. Everything has been fine at 3.5qts.

My engine's sweet spot is between 4-5 qts. 5 and above it starts to spit oil out of the breather.

Many engines it does matter if it’s a tailwheel or not so far as dip stick indicating the correct level. PT-6 for example reads off, if memory serves by two quarts, it reads high.
But as it appears that our little motor tank is round and the stick is pretty much in the middle it may be accurate, plus it was surely designed for tailwheel planes where the PT-6 wasn’t. In the 40’s there weren’t many little nose draggers.

A piston engine aircrafts max oil quantity is derived by how many hours its capable of flying with a full fuel load, take that number of hours and multiply it by the max oil consumption allowed and your not allowed to go below min safe level, so same engine in different aircraft may have different max levels.

Many engines if filled to the max will simply blow out the excess over time through the blow by tube, the IO-360 in my Mooney will blow out anything over 6 quarts, it’s max is 8. Oil consumption above 6 is rapid and the belly is oil covered.

So, what I would do is fill it full, then monitor oil consumption as you fly and if it makes a rather drastic reduction at a certain level, then that’s the level I’d fly it at, but personally I won’t fly with less than 4 myself, my theory is if you spring an unknown leak, your better off with a high level when the leak starts than a low one.

Personally mine doesn’t seem to use much more if full, but then I have leaks too, these little motors as they have a deep sump tank, may not act like their bigger brothers?

I own the STC547EA. Listening to all the comments and questions regarding oil level, I have been trying to find the correct answer. For years I change oil and put in six quarts, in my O-200, and it is happy. For the last year I have used 5 quarts at oil change, to see if the consumption changes. No real difference!
Lycomings on the other hand use more if you fill them all the way. It is because the crankshaft spins close to the oil level. Using a little less makes the consumption less.
On the Continentals, the Sump is well below the the moving parts and the oil has to flow down to the sump.

The bigger Continentals do just like the Lycomings, that is throw out oil above some set level, and interesting to me that level may vary a little from engine to engine.

Lycomings max allowed oil consumption is interesting, it’s based solely on HP

The following formula is used to calculate the maximum allowable oil consumption limits for all
Lycoming aircraft engines.
1. FIXED WING
0.006 x BHP x 4 ÷ 7.4 = Qt./Hr

So a 300 HP Lycoming burning 1qt an hour is airworthy, and going from memory the Continental IO-520 in the C-210 I used to fly was also allowed to burn 1 gt an hour, the 210 carried 90 gl without extended range tanks and would burn about 12 gl an hour at altitude, so theoretically it had an 7.5 hour endurance, and could therefore burn 7.5 quarts of oil, so you can see why that motor could hold 12 quarts when topped off, but above 9 or 10 it woud blow out the excess over time.

Now what Continental says is max allowed for C-85’s or O-200’s I don’t know, but woud be interested in hearing what it is if anyone has a reference, mine leaks more then it burns, I feel sure of that
Is it .4 per hour?
I’ve seen .4 and .6, but neither in a Continental publication.

OK, apparently .4 for the C-85 and .6 for the O-200