Curious oil question

I added 1 quart of oil to my already blackish 6 quarts this weekend before I flew. An hour later while I was filling up with fuel, I noticed some dripping under my plane. It turned out not to be from my plane but while I was checking things out, I put my hand on the inside of the cowl at the exhaust outlet. The oil that vented out of the engine through a hose that exits between the exhaust pipes was fresh oil. That is, clean, not mixed with the rest of the older oil in the engine. It was a little disheartening to see that my newly added oil was the first to be vented out of the engine in flight, as though it never had a chance to mix with the older oil already in the engine.

Does this seem right? Any reason it would happen this way? The only other thing I would not is that the engine was pretty cold that morning when I added the fresh quart. The oil was very slow to enter the engine through the dip stick tube.

Thanks. Andy

dont know why the new oil blew out first, but i never run more than 6 qts in a lycoming. all of mine liked to be right around 6. any more and it just blew it out until it got to 6.

bob burns
RV-4 N82RB

Oil

My engine is similar, anything over 6 on the dipstick just dumps out. So I just check that I have no more than 6 and never have any oil on the belly.

AndyRV7 said:

It was a little disheartening to see that my newly added oil was the first to be vented out of the engine in flight, as though it never had a chance to mix with the older oil already in the engine.
Does this seem right? Any reason it would happen this way? The only other thing I would not is that the engine was pretty cold that morning when I added the fresh quart. The oil was very slow to enter the engine through the dip stick tube.
Thanks. Andy

Click to expand...

Is it possible that you did not allow the engine to warm up sufficiently to mix the oil before going full throttle for take-off?

Dirty oil looks cleaner when it is very thin, like warm on your finger, compared to thick and cold on the dipstick. the suspended carbon makes it dark, so it looks half as dirty if the sample is half as thick.

Some good insight. It was definitely clean oil. The oil temp stayed on the stop (<50*) for a good while after I started the engine. I didn't taxi until it was climbing in temperature. And I didn't do my run-up until 80* (take-off 100*). That's pretty much my S.O.P in the cold weather. I can't say I've stuck my hand under the vent before though. I also target 6 quarts as well (O-375 w/8qt sump). I was down about half a quart at 5.5 quarts when I preflighted. I'll have to have another look under the cowl to see if the oil snuck out of the funnel and down into the bottom of the cowl. But I don't think it did. I watched it pretty good because I was surprised how thick the Phillips 20W-50 XC was that morning in the 30* hangar.