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  #11  
Old 07-21-2017, 10:29 AM
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Quote:
Originally Posted by Jesse View Post
The normal/acceptable oil consumption rate is below 5 Hours per quart to upwards of 20.
More specifically it is given as a maximum in Section 3 of the Lycoming Engine Operating Manual.

It varies by power setting - for a O-360-A model -

Full rating at 2700 rpm - 0.8 qts per hour

Performance cruise (75%) - 0.45 qts per hour

Economy cruise (65%) - 0.39 qts per hour

The economy cruise number would give almost 10 qts used in a 25 hr oil change period. I would be concerned if my engines got close to that..
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  #12  
Old 07-21-2017, 10:55 AM
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Default From Lycoming Service Instruction No. 1427C

From Lycoming Service Instruction No. 1427C

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

For an O/IO-540 260 HP at 75% cruise the limit is .8432 quarts per hour.

TJ
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  #13  
Old 07-21-2017, 01:32 PM
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With that formula, would you run out of gas or oil first
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  #14  
Old 07-21-2017, 02:08 PM
N427EF N427EF is offline
 
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Default From Lycoming Service Instruction No. 1427C

Don't know anyone who would be happy with that kind of oil consumption
but that is what it says in the service manual.
Jesse described a "normal range" for you, mine runs about 14hours per quart.
I guess I am in the normal range.
I would be concerned if all of a sudden my consumption went from current levels to say 5 hours per quart.
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  #15  
Old 07-21-2017, 02:15 PM
rv7charlie rv7charlie is offline
 
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Quote:
Originally Posted by bret View Post
With that formula, would you run out of gas or oil first
See my earlier post about oil pan size.
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  #16  
Old 08-01-2017, 02:53 PM
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Quote:
Originally Posted by ReidVaitor View Post
I asked my engine builder years ago, his response- let the oil go down until it stops losing oil. 6qts is were it stops and loses very little below that mark. I have added more (7qts) on new changes and it keeps the same temps and throws it out most oil quickly than stabilizes at 6.
My temps are 200F +/- 10F at 6 qts in warmer climates
That is my experience and this is what I do...

I put 7 qts in at change time - it registers as 6.5 or so.

At about 40 hours I'll be below 6 qts. If it hits 5.5qts, I add some. Otherwise at 50 hours I change it.

As a by-product, it seems to keep my oil temps above the minimum. I fly out of NC, nuff said.
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  #17  
Old 08-01-2017, 08:21 PM
tim2542 tim2542 is offline
 
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Just another opinion on this subject, but I'll let mine (O-360) burn down to the 5 qt. level, it seems to stabilize there. I won't let it get much lower than that, but I'd be comfortable on a cross country at the level or lower if an oil change is due soon.
It uses ~Qt/15 hrs. so that helps with my comfort doing that.
5qts is well over Lycomings min.
Tim Andres
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