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Old 07-21-2017, 10:29 AM
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az_gila az_gila is offline
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,361

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..
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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Old 07-21-2017, 10:55 AM
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Flying again! Flying again! is offline
Join Date: Aug 2011
Location: Keller, TX
Posts: 355
Default From Lycoming Service Instruction No. 1427C

From Lycoming Service Instruction No. 1427C

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.

RV-10 N331JH 3rd owner (First flew in 2005, #15 flying)
Northwest Regional 52F
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Old 07-21-2017, 01:32 PM
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bret bret is offline
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Location: Gardnerville Nv.
Posts: 2,767

With that formula, would you run out of gas or oil first
7A Slider, EFII Angle 360, CS, SJ.
2018 gladly supported
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Old 07-21-2017, 02:08 PM
N427EF N427EF is offline
Join Date: Oct 2005
Posts: 1,510
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.
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 400 plus hours
Over 2500 Gallons of E10 mogas burned
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Old 07-21-2017, 02:15 PM
rv7charlie rv7charlie is online now
Join Date: May 2006
Location: Pocahontas MS
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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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Old 08-01-2017, 02:53 PM
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MauleDriver MauleDriver is offline
Join Date: Aug 2006
Location: Lake Ridge Aero Park - Durham NC
Posts: 164

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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Old 08-01-2017, 08:21 PM
tim2542 tim2542 is offline
Join Date: Aug 2009
Location: Redding,Ca
Posts: 598

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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