Oil Level

[Jose L. Ichaso]

What is the minimum oil level in the engines for a safe operation, since the original manuals says 7 qts. and when I use 8 Qts. seems it goes out by the breather. Can you operate with as low as 6 qts?

[SkyKing]

Jose,

I think you forgot to tell us what YEAR and MODEL series of Skymaster you're referring to.

The POH for our 1977 Pressurized model has this to say concerning capacity of engine sumps:

"Do not operate on less than 6-quarts for each engine. To minimize loss of oil through breather, fill to 7-quart level for normal flights of less than 3-hours. For extended flights, fill to 8-quarts."

SkyKing

[kevin]

Both my '65 337 and my '73 P337 seem to exhibit the same behavior (and this is my second set of engines on the '73).

Fill the sump to 7 quarts after an oil change. On the engines I've had (and have now), I see a fairly quick drop (sometimes just one flight) to 6 - 6.5. Another couple of flights it drops to somewhere between 5 and 6. On my current engines, the rear stops at just above 5, the front at just below 6. And there it will stay for 20 hours or so, with very slight drop perhaps, until the oil starts to get a little old, and begins to burn a little. I change oil every 25 to 35 hours (goes longer if I am away from home, I wait to get home to change it).

From this experience, and on the advice of my fright instructor/A&P who flew checks in Skymasters for 500+ hours, I wait for my rear engine to go below five before adding (I always add 1 quart at a time), and I wait for my front to get to 5.25 or so.

This is not what the POH says, so remember this advice is worth what you paid for it, and you make the decision whether to follow it or not. But it has worked for me for six years. Front engine on last set went to 1700 hours, was still going strong...

One exception. If I am flying in very hot weather, ambient on the ground above 85 to 90, I might add a quart at about 1/2 quart higher than the numbers above, just to keep the oil a little cooler during climb.

My two cents. We'll see what others have to say...

Oh, P.S. I still get small amount of oil on the belly and rear engine lower cowl. But nothing much...

Kevin

[Bob Cook]

Kevin

I add oil after 6 qts in 1/ qt increments. I burn about 1 qt in 20 hrs. No oil on belly other than residue and none on the tailfeathers. I try and hold it around six and if going for an hour or two then will take off with six. Any more then seven it "evapourates" quickly. In fact I think it is blown back into the engine by way of seperator.

The engines are both relatively new tcm remans with 3250 hrs on them over past year and half.

I change oil when convenient btween 25-30 hrs and at 50 I change the filter. Also feather engines on ground when doing the 50 hrs change to turn over the prop oil.

fyi

Bob

[Jose L. Ichaso]

Thank You for your response, mine is a 1969 337D, with engines very close to TBO, burning 1 qt. every 5-6 hours, from 8qt to 7qt oil level. I will try know to 6 qt. minimun level, since I always operate in very hot conditions 80 to 90 F°.