Oil Consumption Pirep

[INA201]

I was always a little concerned that my oil consumption was a little high at 5-6 hours a quart.  I checked the exhaust pipe for burning oil.  We checked the plugs. Compressions were always good.  Did not have an abnormal amount of blowby.  Everything checked out.  Weird thing is, I didn't have much of an RPM drop when doing the mag check.  I get my D mag rebuilt(500 hour) and poof oil consumption has dropped.  I've put about 1 1/2 quarts in about the last 18 hours.  Consequently, I get a 70 RPM+-  drop during my mag check.  The oil is also staying more honey looking.  Go figure.  I thought I would throw this out there because I haven't heard of this scenario before.

[Bartman]

Wonder if it was leaking around the Magneto gasket ???

[INA201]

4 minutes ago, Bartman said:

Wonder if it was leaking around the Magneto gasket ???

No leaks other than a few drops from the pushrod seal.

[takair]

Do you have an air/oil separator?  Perhaps it was not quite set up correctly before?  Really odd that just a mag swap would fix this without an obvious leak.  Any chance your mag timing was reduced?  Wouldn’t think it would make a big difference either, but...

[carusoam]

Any change of flight habits?

More long X-countries, fewer T/Os and landings...

More Longer high powered climbs to higher altitudes...

Lower level of fuel used 5.5qts in place of 7?

These are things related to pushing oil out the case vent.

 

these are the things that effect measurements...

Take written notes for a while... to see if changes show up...

Measuring technique, location that the measurements are taken, type of oil used, or the case of oil used...

 

Best regards,

-a-

[Bob - S50]

Any chance when they put the magneto back in that they timed it to 20 BTDC instead of 25 BTDC?

[INA201]

21 minutes ago, takair said:

Do you have an air/oil separator?  Perhaps it was not quite set up correctly before?  Really odd that just a mag swap would fix this without an obvious leak.  Any chance your mag timing was reduced?  Wouldn’t think it would make a big difference either, but...

No separator installed.  Please feel free to call me crazy.  I had the same consumption for three years.  I'm expecting to burn a little more as the oil ages but even so it is a very noticeable change. I always keep a close tally on how much oil I have used.  I did have a small induction leak fixed and the exhaust tightened up at the same time.  The biggest thing was almost no mag drop prior to the mag being rebuilt.  

[FoxMike]

Might be the oil control rings are worn-out.  Compression  test will not normally reveal worn oil control rings.

[wpbarnar]

1 hour ago, Bob - S50 said:

Any chance when they put the magneto back in that they timed it to 20 BTDC instead of 25 BTDC?

Good point.   Minimal mag drop can be an indicator of advanced timing.   Also advanced timing increases cylinder pressure.  Would not have thought it could make that big of difference in blow by and oil consumption,  but maybe....

Blow by also contributes to oil going black faster.  You indicated that it was staying honey colored longer...

Edited December 7, 2018 by wpbarnar

[Piloto]

Oil amount in the sump depends on the time elapsed after shutdown and ambient temperature. The longer the time after shutdown the more  oil will drip down from the engine top to the sump. At warm ambient temperatures the quicker the oil will drip down. I always measure the oil level at least one week after shutdown.

José 

[kortopates]

Spurious correlation!


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[INA201]

I’ll determine total usage for 30 hours which used to be around 5 quarts +- a little and see where I am.  I do wait for a few days before relying on an accurate reading.  The blow by I get now on the front gear door is very fine of virtually no significance whereas before I may have had a little more and a streak or two.  The blow by was never really significant but a noticeable difference right now in my opinion. I better wait for a couple of oil changes,  50 to 60hours or so,  to make a more accurate determination on usage.  I do agree with the spurious correlation because from what I know it doesn’t seem to be a correlation that I have seen or read about with just these changes to the engine.

How far forward can timing be set. Could it have been set to 30tdc for example? 

Gimme a couple of months and I’ll update the data as well.

[Bob - S50]

4 hours ago, INA201 said:

How far forward can timing be set. Could it have been set to 30tdc for example? 

Gimme a couple of months and I’ll update the data as well.

If the timing was set that far in advance, I would guess the engine might not even run and if it did you might do some serious damage to it.  I'm thinking the magneto is more ...retarded... than it used to be.  That is, 20 now vs 25 before.  That would cause peak pressure to occur further after TDC which would reduce peak pressure, reduce CHT, maybe increase EGT, and reduce blow-by.

Unless you meant that you thought it was too advanced before and is set properly now.

Edited December 7, 2018 by Bob - S50
typo

[kortopates]

Timing should only shift a max of2-3 degrees, if even that much, between annuals. And when external engine timing is shifting, so is internal magneto timing and about the max for internal timing to shift before spark really weakens is ~4.5 degrees.


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