Oil Consumption; what's considered "Normal"

[PTK]

M20J, IO-360-A3B6D,  Aeroshell 15W50.

This may have been discussed in passing before for different engines. But I was wondering what is considered 'normal' oil consumption. Obviously there will be oil consumed by our air cooled engines and an engine can have high oil consumption. But is there such a thing as too low?

My most recent reading is 1 qt in 11.3 hours. This is typical for my engine.The funny thing is I changed the oil before a long trip a few weeks ago and serviced it with 8 qts. 11.3 hours later it’s at 7 qts. If some of that 1 qt was blown out then the oil actually consumed in combustion would be less. IOW it would be 1qt in something >11.3 hours!

[INA201]

2 hours ago, bluehighwayflyer said:

I’ll be interested in reading others’ experiences, but I think a quart every 8 to 10 hours is pretty typical in our Lycomimgs, Doc. The now high time engine in my J has used a quart every 5 or 6  hours, though, the whole time I have owned it (600 hours) with no appreciable change in consumption or other signs, so I’m not too worried about it. It sounds like yours is doing great. I find that my oil consumption increases as the oil gets dirtier. I believe in shorter than recommended change intervals. 

Jim

My 1978J 900smoh uses 5 an hour with pattern work and 6-7 on longer trips. Has been that way for two years with no signs of blow by or burning oil.  Good oil analysis etc.  I use 100W plus without camguard but considering trying the Phillips/camguard combination.  This seems to be a quite common usage level.

[markejackson02]

I use a quart every 5-10 hours, depends on the kind of flying.  Anything over 6-6.5 qts gets blown out usually fill it when it gets below 6.

[ohdub]

Mine burns a quart every 4 hours. Cylinders have been borescoped showing no issues, compressions are good, oil analysis also good, it just seems to be what the engine consumes. Engine has 1,100 his since new and I've had it for the last 250 hours.

[EricJ]

I'm throwing this out hoping somebody has some pertinent thoughts:    I'm on week two of ownership of my airplane, but it's history over the last ten months or so is known.   When it was ferried from AZ to Maxwell's in TX the first leg used a lot of oil, it was refilled, and then it used more or less none the rest of the way.    This has become a fairly consistent theme:  it either uses a crap ton of oil (probably a quart every 1.5-2 hours), or very little.  Last week I flew it from AZ to SoDak and back, with fuel stops both ways at about the halfway mark.  In both directions it used two quarts during the first 3 hour leg, and no appreciable oil during the second 3.5 hour leg.   That was always starting at 6qts.

It does leak, but not that much.   In SoDak a local shop found that the oil temp sensor had been over-torqued and the copper crush gasket was badly distorted.   They replaced it, but there was still oil down the right nosegear door and in the nose wheel well on the way back, so there are other pending leaks.   There's no appreciable filth behind the breather tube, and the exhaust pipe goes from sooty black to dark grey depending on how it's feeling (it's kind of a nice grey now, after the last 3.5-hour non-oil-burning leg).

There are still leaks, but I don't think that accounts for the massive loss.  I'm suspecting maybe a flaky valve seal?   Compressions have consistently tested good to very good on the motor during annual in the spring and at Maxwell's last month.

[jaylw314]

Mike Busch has a webinar discussing this

The upshot:

Very low oil consumption (20 hours/qt) MIGHT be a sign not enough oil is getting to the cylinders.

Very high oil consumption (1 hour/qt) MIGHT be time to check the cylinders.

Anything in between PROBABLY is perfectly fine.

[jaylw314]

5 minutes ago, EricJ said:

I'm throwing this out hoping somebody has some pertinent thoughts:    I'm on week two of ownership of my airplane, but it's history over the last ten months or so is known.   When it was ferried from AZ to Maxwell's in TX the first leg used a lot of oil, it was refilled, and then it used more or less none the rest of the way.    This has become a fairly consistent theme:  it either uses a crap ton of oil (probably a quart every 1.5-2 hours), or very little.  Last week I flew it from AZ to SoDak and back, with fuel stops both ways at about the halfway mark.  In both directions it used two quarts during the first 3 hour leg, and no appreciable oil during the second 3.5 hour leg.   That was always starting at 6qts.

It does leak, but not that much.   In SoDak a local shop found that the oil temp sensor had been over-torqued and the copper crush gasket was badly distorted.   They replaced it, but there was still oil down the right nosegear door and in the nose wheel well on the way back, so there are other pending leaks.   There's no appreciable filth behind the breather tube, and the exhaust pipe goes from sooty black to dark grey depending on how it's feeling (it's kind of a nice grey now, after the last 3.5-hour non-oil-burning leg).

Could it be from the propeller?  That might fit the inconsistent amount, since you may be flying different flight profiles?

[Hank]

My C, with O-360, gets 12-15 hours on the first quart after I change it (fill with 7 quarts, 6 for the engine plus 1 for the filter). Each succeeding quart seems to last a little less than the one before it. I change every 50 hours with AeroShell 15-W50 with no extra additives (don't think I drip much sweat down the filler tube . . .)

[StevenL757]

16 minutes ago, Hank said:

My C, with O-360, gets 12-15 hours on the first quart after I change it (fill with 7 quarts, 6 for the engine plus 1 for the filter). Each succeeding quart seems to last a little less than the one before it. I change every 50 hours with AeroShell 15-W50 with no extra additives (don't think I drip much sweat down the filler tube . . .)

Have you thought of moving your interval from 50 to 25-30 hours to see if the behavior changes?  Based on experience with several 4 and 6-cylinder engines, I find 50 hours - even with long trips in between intervals - is far too long between changes.

[Hank]

Just now, StevenL757 said:

Have you thought of moving your interval from 50 to 25-30 hours to see if the behavior changes?  Based on experience with several 4 and 6-cylinder engines, I find 50 hours - even with long trips in between intervals - is far too much.

I've put over 600 hours on the tach this way, and the 200 TSOH when I bought it were the same. And based on a question from a stranger on the internet, no, I'm not inclined to change my maintenance practices. Given knowledge, reputation and data, I would peruse the data,  consider the knowledge base and think it over.

This is not meant to be offensive, but I don't know you, your training, experience or anything outside of the post above. I used to change the oil in my cars every 3000 miles (when the manufacturers were recommending much longer); now that they are advertising 7500 mile or greater oil changes, I do it every 5000 miles and laugh at the ads from the quick oil change places trying to frighten me into 3000 mile intervals because the driving I do is "harsh environment" as if I'm a taxi driver.

[StevenL757]

Wasn't trying to act like an authority or undermine your maintenance habits, Hank.  There are many on here with tons more experience than my 32+ years' flying, so was merely passing on my own experiences, and asking about yours in an attempt to learn more about how you and others manage their airplanes.

Back to Peter's original post - Peter, what oil do you use to get that level of performance?  To answer your question, I see between 10 and 12 hours to a quart, and for longer trips, closer to 14 hours to a quart using Exxon Elite 20W50.

Steve

[PTK]

4 hours ago, StevenL757 said:

Wasn't trying to act like an authority or undermine your maintenance habits, Hank.  There are many on here with tons more experience than my 32+ years' flying, so was merely passing on my own experiences, and asking about yours in an attempt to learn more about how you and others manage their airplanes.

Back to Peter's original post - Peter, what oil do you use to get that level of performance?  To answer your question, I see between 10 and 12 hours to a quart, and for longer trips, closer to 14 hours to a quart using Exxon Elite 20W50.

Steve

Steve, I use Aeroshell 15W50 and change it q 30 hrs approx. on the high end. Usually it’s closer to 25 hours. I feel good knowing there's clean fresh oil in my engine. As far as the cost Δ it adds maybe 25$ to each oil change by changing it more frequently. It’s a no brainer!

[Oldguy]

My "normal" consumption averages ~8 hours per qt. The first quart takes longer and as the oil gets older, it goes quicker. (Isn't that the way with everything?)

I run Phillips with CamGuard in my almost 1600 hour factory reman A3B6D engine and rarely get my oil above 200 DF.  The oil gets changed on either engine time (35 hrs.) or calendar time (4 mos.). AVLAB analysis on each change with consistent numbers since the engine was IRAN'ed at about 400 SFRMN for high copper (prior to my owning the plane). The fullest the engine gets is at oil change with 7 qts. of oil and the CamGuard. After that, anything below 5.5 on the dipstick gets an oil/CamGuard addition to get it above 6.

[Piloto]

I noticed that oil consumption varies with engine RPM. The lower the RPM the lower the consumption.

José 

[Bob - S50]

5 minutes ago, Piloto said:

I noticed that oil consumption varies with engine RPM. The lower the RPM the lower the consumption.

José 

I'm beginning to think it is more related to MP than to RPM.  The lower the MP, the lower the blow-by, the lower the consumption.  On the other hand, if you are burning the oil...  So I guess it depends on the individual airplane.  The only way to know is to experiment and see what works.

[Piloto]

Just now, Bob - S50 said:

I'm beginning to think it is more related to MP than to RPM.  The lower the MP, the lower the blow-by, the lower the consumption.  On the other hand, if you are burning the oil...  So I guess it depends on the individual airplane.  The only way to know is to experiment and see what works.

On M20Js there is only one throttle setting for cruise, full open. So the only other option is RPM setting.

José 

[Bob - S50]

12 minutes ago, Piloto said:

On M20Js there is only one throttle setting for cruise, full open. So the only other option is RPM setting.

José 

Maybe for you.  But at low altitudes, I do not run WOT.  If I'm below about 6000', I run less than WOT.  I am not one to run WOT and then go LOP enough to limit the power.  I prefer to run about 10-30 LOP and use the throttle/prop controls to limit my power.

[kevinw]

I just had my J in the shop to get the Tanis heater repaired and had the oil changed while the cowl was off. I use 7 qts of Phillips x/c 20w50 plus camguard. We talked a lot about oil consumption and intervals. I'm using about a quart to every 8 hrs. He advised changing the oil every 25-30 hrs, don't add until it gets below 6 qts and to consider running a lower rpm. I run wot and 2500 at altitude. He said running it at 2400 should slow down the consumption. I just had this done so I can't say if this helps yet. I've been changing the oil at about 35 hrs previously.


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[Bartman]

On my J we discovered a leak at one of the bolts going thru the case which we plan on addressing at annual in a couple of months. After discovering the oil on the belly was due to the leak and not coming out the crankcase breather like I thought I changed from 15w50 to 100W Plus, and at oil change add 8 with new filter, and keep her at 7 on the dipstick. I decreased my cruise RPM to 2400 since discovering the leak around June. Even with keeping more oil on the dipstick and despite the leaking bolt I'm improved to a quart every 5-6 hours which I attribute to decreas in cruise RPM from 2,500 to 2,400 but thicker oil didn't hurt either. Change oil and filter about every 35 hrs. 

[glenn reynolds]

Since we are having fun telling oil stories, I'll throw mine into the library:  cont 550 no turbo. (ovation).  I bought the plane with 150 hours on a factory new engine and the darn thing threw a quart out the breather every 3 hours regardless whether you put a full sump of 8 quarts, partial sump of seven quarts or started the flight clock with the minimum of six quarts.  I did actually see a slight improvement to about four hours when I started trips with only six quarts, but what a lot of nice clean oil all over the belly.  Lots of sage mechanics all said, bad break in, live with it.  During a routine oil change a leak at the accessory pad was resolved (new gasket) and the leak was putting a pretty good film of oil on the firewall, but was a relatively new issue.  during this oil change the service team made a mistake and overfilled the sump to nine quarts.  Since I was now a trained belly cleaner, I flew the plane rather than decant the extra quart.  All opinions were that the extra quart would be blown out and we would carry on with the usual quart per three hours of operation.  but no.... it was not to be.  I now have 14 hours on the same nine quarts!  Yup you read that correctly.  when i maintained between six and eight quarts in the sump, the engine would blowing a quart every three and a half hours.  When the sump was accidently overfilled to nine quarts it's held that nine quarts for 14 hours and counting.  Just to be clear, I'm not complaining, and I'm really not interested in "experimenting" as now that I have had the airplane for 14 months and this is the first month with out me under the belly cleaning oil! But, I am really curious as to why and theories are cheap.  

[carusoam]

Start the theory with...

Normally, IO550s go a lot longer before a quart goes missing compared to an IO360...

Looks like the extra quart is interupting the high oil useage...

Report when the extra quart is gone, followed by what happens next..?

PP thoughts only, not a mechanic.

Best regards,

-a-

[PTK]

Tony, I think there’s truth to a higher volume interrupting usage. Although subjective, I have experienced this as well. I used to subscribe to the “don’t fill it to 8 qts because it will blow it out” notion. Until recently when I put in 8 qts and it took 12 hours to drop to 7! And this was oil used by the engine and not blown out! My belly has been traditionally clean of oil. I am keeping close tabs on this and will be able to make an objective determination as I build more empirical data.

Incidentally, I cruise at 2450 RPM because prop is dynamically balanced there and WOT. The only time I come off of WOT is when I setup to land. 

[rxo188]

One quart every 6 hours. Plus or minus an hour. I never put more than 7 quarts in, as they'd be blown out. Compression is good. I logged about 900 hours on this engine, which is about to reach 1000SMOH.

[jlunseth]

Well here's my story.  When I first got my 231 it consumed a fair amount of oil.  Let's say 1 qt. in 10 hours, although it has been so long that I don't really remember with exactitude.  I asked the same question, what is normal.  I heard all the normal explanations, its a Continental, the cylinder seal is not very tight, its normal etc.  It got to the point where I would use a quart for a long trip, say 4.5 - 5 hours, still was told that's just normal.  We had some small leaks, mostly rocker covers.  Then I had an incident which I have written about here, where we blew almost all the oil out, resulting in an emergency descent to landing in Can.  A small piece of plastic had gotten lodged in the quick drain, there was virtually no evidence on the ground, but in the air with the engine running and pressurized, we were blowing oil out.  Within a couple of years I had the engine IRAN'd, and all the small leaks were fixed. It used to be normal to have a number of chafe leaks at the top of the cowling.  I still get one occasionally, but not much and not big.   Now it is normal to go through an oil change cycle of 20-30 hours without adding oil, and if I am flying alot and go 40-50 hours between oil changes, I might need to add a quart.  Now, during that cycle the oil level will have dropped a quart or so.  That's about what I use now, 1 qt. per 20 hours.  

I have heard all that "stuff" about oil usage, and certainly the old radial engines burned through alot.  But I no longer buy the idea that a quart in 6 or 8 hours, or even 10 hours, is normal.  Maybe on a different type engine than my TSIO360LB it is normal, but if I get to that level again I will be looking for the problem in the engine.  

[jlunseth]

PS the other sort of weird oil issue is when did you check it.  I can't tell you how many guys have expressed concern to me about their oil usage, they checked it before they flew, did a short flight, then check it after and it is down a quart and a half!!  What do I do???  Well duh.  For those who don't understand what I just said, and I hope there aren't any, the oil settles out of the engine when it sits, and your highest oil level will be before the engine is started.  It only takes seconds for that "extra" oil to get pushed into the engine and voila, you are "down" a quart.  Patience with new owners, we were all one once.