Oil usage

[Timothy Barnett]

I have a '69 260 and experiencing some blow by with the oil. Seems to me to be somewhat excessive with a quart every 5 hrs. Once suggestion I have been given is to install an oil/air seperator. Any suggestions pro or con with this idea? Also, can anyone suggest the appropriate brand/item for this engine?

[William Hughes]

I have found that any amount of oil in the engine (PA-24-250) above 7-1/2 to eight quarts blows out onto the belly asap. Once I got used to leaving it at 7-1/2 to eight quarts it stopped blowing out the oil and now I'll add a quart every 15 hours or so. I have to screw up my courage to let the oil get down to 6-1/2 quart though, but if I add any sooner it just seems to blow out the breather tube right away.

I noticed you mentioned blow by - may I inquire what you meant by that term?

[Timothy Barnett]

William, thanks for the insight into the oil usage with the Comanche. After more extensive reading, I think your advice and information seems to be exactly what I am seeing from everyone else. I will try to let the oil level stay closer to the 7 quart line. As for the comment on blow by, that is just my way of saying what you were saying. Oil level is dropping because the engine is blowing excess oil out on the belly of the plane.

Thanks for the help.

[Charles Schefer]

I second William's comment / suggestion with regard to any horizontally opposed air cooled piston aircraft engine. On the Cirrus with the IO-550 we've found anything above 6qts on the dipstick blows out on the belly almost immediately. On my PA-30 I keep the oil around 6 qts on the dipstick - same reason.

Keep in mind that there's more oil in the system than what you read on the stick. On the Cirrus we put 7 qts in at the oil change yielding 6 on the dipstick. A quart is taken by the filter, lines and "in suspension" in the engine. If we don't fly for a few weeks more drains down and the reading may go from 6 to 8 on the stick. Run the engine and it's back at 6. On the PA-30 similar situation but since I installed Air Wolf remote filters, which are larger -109 filters instead of stock -108, the system takes up 2 qts beyond the reading on the stick. I put 8qts per side yielding 6 on the stick.

For twin owners always remember that for the same volume of oil in each engine the left engine will show 1/2 - 3/4 qt more on the dipstick due to the stick position on the right side of the engine and the angle of the engines due to the dihedral of the wings. There are other threads on this.

- Charles

[William Hughes]

I hadn't thought of the oil up in the engine but I'll keep an eye on that as well. I had been scratching my head about that issue.

I mean, if it sits for a week the engine will show more oil. If I then fly it on a long weekend for a long trip, say four or five three hour legs, then the oil will drop a quart. If I let it sit for another week, then back up it comes.

That makes all sorts of sense now that you mention that the oil could take a few days to actually all drain right down.

[Charles Schefer]

It does indeed drain down. Cirrus flys very regularly but as an example... In May it sat for 3 weeks. The oil went from 6qts to 8qts on the dipstick. After a short flight it read 5 & 1/2. It's also important (IMHO) to not check the oil - or I should say not take the dipstick reading precisely right after flight. With multiple legs it's good to check the dipstick but right after flight the reading will be down quite a bit. The next day it will be back to normal (say 6) then after a few weeks of sitting it will be at 7 or 8...

[Alan Cheak]

Tim:

Just for your reference the term blow by is usually referred to a condition were your rings in one or more Pistons are not seated tight enough so that oil and heat is blowing by the cylinder walls and is effectively cooking your oil inside the crankcase. While your oil consumption will go up, the most tell tell sign is that your oil will be pitch black after an oil change and within a few hours. I have this problem too, but my engine is over TBO so I just change my oil every 25 hours or so until I'm ready to do the overhaul.

Alan