Maximum oil consumption

This list is getting a little quiet, so I thought I'd try to stir up the nest a bit!

I just read this on another forum:

The following data is taken from the Approved Lycoming Overhaul Manual
available from Lycoming. Note that the maximum consumption allowed
varies according to the model and is based on consumption at full rated
horsepower and maximum rated rpm. All data is at maximum oil inlet
temperature of 245 degrees Fahrenheit:

From what I've read, Subaru-powered aircraft owners don't need to add oil between changes (25-50hrs). I know I've never added oil between changes in any car I've owned since the 70s.

One less thing to think about when flying with a Subaru, at least.

Nice try

That is for break-in buddy not normal operations.

This is also a max. Most break-in engines do not start this high. This is a guide for the engine builder when breaking in to make sure there is no major problem. Just a guide and just for break-in, so don't get so excited or smug. We will have to call all the children in from the play ground for a SMUG alert. I know you want to go, Na-nana-na, at us Lycoming drivers, but it's I that goes Na-nana-na-naaaa.

Mickey this is MAX oil use for initial break-in, e.g., the first hour or two of operation. Break-in can take different times depending on the jug material and finish. The hardest is chrome, and they can take 25-50 hours to break-in. In that time oil use continuously goes down until break-in is complete and nominal oil use is achieved. During the life of the engine, oil use remains on average fairly flat. It might drop off towards the end, but not necessarily.


Every Lyc I have flown used a qt in 12-18 hours, and some of them where over 2000 hours! Stir away.

If it was a Qt in less than 1.5 hours as you say, I would not fly it. That is clearly a problem and unusual.

I would get concerned or tired with a qt in 8 hrs. That is lowest I have ever heard of from another pilot. I suspect he had a worn valve guide. It only takes one. Valve guide wear can be traced to poor pilot operations, poor maintenance.

There are two places (Mahlon help) that causes the oil use: Valve guides, oil control rings. If compression or oil use is unacceptable, the offending jug is pulled off and repaired. The good news is the engine remains mounted with most controls and lines connected to the engine. Pre-TBO repair is the exception not the rule. The top end should and does routinely go to TBO.

If you need a top end repair, it's most likely for dis-use, where rust and corrosion occur or mis-use, running way over 400F CHT too much. Next on the list is poor maintenance like lack of oil changes. Fly with in limits and frequently you will go to TBO with no un-scheduled major maintenance, bet on it. Oh yes, your oil consumption will be in that ball park I mentioned, nominal 12-18 qt/hr.

Any one feel free to write Lyc about this or any question. Lyc does not post max use for normal OIL use and operations, but the ones you mention are for initial break-in, the first hour, not post break-in. At one time I was flying from a fleet of 30-40 Lyc powered planes as a Freight pilot and CFI for a few years. They where all very reliable and economical, as long as you flew regularly and took basic care of them. I don't recall any plane being taken off line for a top overhaul, ever. Don't buy into the urban legend and exaggerated horror stories. There's no reason you can't get 10-20 years of GA flying (+2000 hours) with your Lyc before overhaul with just basic maintenance. I know of at least three Lycs flown to 2,600 hours. For most GA pilots that is a lifetime of flying.

To stir the pot:
Why do alternative engine users need to pick on the venerable Lycoming to feel good about their alternative engine choice? I'll guess it's a compliment that the Lycoming is the epitome, standard by which all other judge themselves from. Keep working, some day you might almost be as good as a Lycoming.

gmcjetpilot said:

That is for break in buddy not normal operations. This is MAX oil use for initial break-in, e.g., the first hour or two of operation.

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Good info - I didn't know that. I've never flown a lyco that used anywhere near as much oil as the numbers above show. I was surprised to see Lycoming call these rates of burning oil "normal".

gmcjetpilot said:

To stir the pot:
Why do alternative engine users need to pick on the venerable Lycoming to feel good about their alternative engine choice?

Click to expand...

Because it's just plain fun to see you hornets buzzing around telling us how crazy we are!

Not so fast George....

gmcjetpilot said:

That is for break-in buddy not normal operations.

This is also a max. Most break-in engines do not start this high. This is a guide for the engine builder when breaking in to make sure there is no major problem. Just a guide and just for break-in, so don't get so excited or smug. We will have to call all the children in from the play ground for a SMUG alert. I know you want to go, Na-nana-na, at us Lycoming drivers, but it's I that goes Na-nana-na-naaaa.

Mickey this is MAX oil use for initial break-in, e.g., the first hour or two of operation. Break-in can take different times depending on the jug material and finish. The hardest is chrome, and they can take 25-50 hours to break-in. In that time oil use continuously goes down until break-in is complete and nominal oil use is achieved. During the life of the engine, oil use remains on average fairly flat. It might drop off towards the end, but not necessarily.

Click to expand...

Actually George, this is the maximum (0.80) recommended by Lycoming for Normal Operation, not break-in.

The "kicker' is that is is for continuous running at 2700 rpm.

If you are at 75% power, the number is 0.45 qts./hr
If you are at 65% power, the number is 0.39 qts./hr

These numbers are for O-360-A and -C models and are taken directly from the Lycoming Operators Manual... always the best reference for real numbers.... even if my manual (May 1996 revision) is 0.02 more that the number quoted above in the original post...

However if my O-360-A4K got to 0.4 qts/hr in cruise, I would be very concerned...

gil in Tucson

MAX allowable and typical oil use are different things?

az_gila said:

Actually George, this is the maximum (0.80) recommended by Lycoming for
Normal Operation, not break-in. gil in Tucson

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Actually you are right, Thanks!

However there are a few mixed signals from Lycoming.

From experience I know what they typically burn, but here is my sources.

What Mickey posted IS the break-in table, because it matches
the Table I'm looking at this very second, Section 9, test procedures,
overhaul manual - Avco Lycoming Direct Drive Aircraft Engines, Page 9-2:

Table 9-1 Engine Run-In Test Limits.

In this TEST LIMIT table it list the same 0.78 Qt./Hr., for example, on the
O-360 -A, -B, -C, -D.



The second Lyc publication is "Service Instructions" - 1427B

"Textron Lycoming Reciprocating Engine Break-In and Oil Consumption Limits"

Here is an except of SI 1427B from Lyc's FAQ:

http://www.lycoming.textron.com/mai...Reprints/maintenance/reciprocatingEngine.html


According to SI 1427B, the formula for max oil use for any Lyc is:

.006 x BHP x #Cyl / 7.4 = .006 x 180 x 4 / 7.4 = .59 Qt. / Hr. >>>> 1.8 Hr. / Qt.

That sounds a little more realistic but very high.


Lycoming's other comment on MAX oil use is to "look at the operating manual",
which you are saying list max allowable use at 0.80 Qt. / Hr. OK, cool I did
not know that, and it is backed-up by my favorite engine site, Sacramento
Sky Ranch. Apparently 1 Qt. / Hr. is an industry standard or rule of thumb for
MAX oil use. It also says 1 Qt/Hr is a little high for a 4 cyl Lyc, so from the
formula above, .59 Qt. / Hr's is about right. As a personal MAX., even 4 or 6
times less oil use than that number would get me worried.

The bad news with high oil use is not only are you pouring oil down the pipes,
you are burning it and causing deposits, plug fouling, which is more bad news.

I guess Lycoming does not want to tie operators hands by virtue of oil use
alone. As long as temps and compression are OK, the oil use is tolerably? Now
I'm really confused. Thanks A lot.

Bottom line there is a big difference in MAX allowable and actual, nominal or typical.