Oil Consumption Data

As I was filling out the Valkyrie's activity log after this afternoon's flight, I realized that as an engineer, I was falling down on the job. I've been writing down every drop of oil and every gallon of gas after every flight since "hour zero", and have never done a thing with any of the data. (I can see the rest of the engineers nodding out there....you're all writing this stuff down as well - right?)

I brought the log home with me, and decided that typing in all of my fuel data was too much of a pain, but oil consumption was another matter. It only took about ten minutes to type in the hours and quarts, and Excel produced the following chart - Oil Consumption (in Hours/Quart) versus hours on the engine. You can easily see how the engine broke in, and has settled on about 8 hours to the quart. That's just about what I had figured - a case of oil every 50 hours. Add six at the oil change, and put in another six before the next change.

It will be interesting to continue tracking it over the next 400 hours....



Paul

Paul have you noticed that when you initially change the oil the hours flown will go quite a while before it uses any? My engine will go 17-20 hours without significant usage and then I'll have to put in 1 quart. Around 25 hours or so and it is ready for some if not another full quart. Then at 30 it all comes out and the 17-20 hour cycle begins again. I don't know if it is the oversquare thing or not, but the oil seems to break down and then the usage goes up. Any ideas? (AeroShell 100+)

Regards,

Same Here Bryan!

I have an O-360 on an RV-6A with around 740+ hours. I have been using Aeroshell 100+ also.

My engine oil consumption is very similar. I usually have to add a quart between changes (25 hours) and it is usually around the 17 to 20 hour mark. I really hadn't thought that much about it, but now you have me wondering why.

Any thoughts from the engine specialists out there would be appreciated.

Wes Hays
N844WB
Winters, TX

Bryan - I looked at the data again, specifically at the intervals between quarts, and don't see a pattern strong enough to say that I'm seeing the same thing you are. If I look hard enough, I can see a few slightly regularly spaced gaps right about the "50's" of hours, where I do oil changes, but that is because I stop adding oil when I am about to do a change, and will let it drop slightly lower than normal.

I also found it interesting that up until 200 hours, I would put in 7 quarts at a change, then let it go down and maintain it between 5 and 6, whereas AFTER 200 hours, I only put in 6 and maintain it between 5 and 6. The graph smooths out a little at that point - not sure what that is telling me, but the engine is definitely happy between 5 and 6.

Paul

Paul, interesting data. And while I "are" an engineer, I quit writing down when I add oil a few years ago. I do make mental notes of each quart added, so that in my mind I know how long since the last "full" time.

There is another variable, which is how we decide when it is time to add a quart, i.e., where on the stick exactly the mark is. Sort of our "comfort" level. I will let it get down to 6 quarts when I'm nearing an oil change. I don't see any change in consumption rate from 8 down to 7 vs 7 down to 6. Both are in the 8 to 12 hour time frame, depending on OAT's.

AlexPeterson said:

Paul, interesting data. And while I "are" an engineer, I quit writing down when I add oil a few years ago. I do make mental notes of each quart added, so that in my mind I know how long since the last "full" time.

There is another variable, which is how we decide when it is time to add a quart, i.e., where on the stick exactly the mark is. Sort of our "comfort" level. I will let it get down to 6 quarts when I'm nearing an oil change. I don't see any change in consumption rate from 8 down to 7 vs 7 down to 6. Both are in the 8 to 12 hour time frame, depending on OAT's.

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I feel perfectly comfortable down to 6, knowing of course that the engine will run down to 2.

Ironflight said:

Bryan - I looked at the data again, specifically at the intervals between quarts, and don't see a pattern strong enough to say that I'm seeing the same thing you are. If I look hard enough, I can see a few slightly regularly spaced gaps right about the "50's" of hours, where I do oil changes, but that is because I stop adding oil when I am about to do a change, and will let it drop slightly lower than normal.

I also found it interesting that up until 200 hours, I would put in 7 quarts at a change, then let it go down and maintain it between 5 and 6, whereas AFTER 200 hours, I only put in 6 and maintain it between 5 and 6. The graph smooths out a little at that point - not sure what that is telling me, but the engine is definitely happy between 5 and 6.

Paul

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My limited experience with the 0360 evolved to the same conclusion - 8 qrts at a change was a waste of 2. The engine got rid of those top 2, probably through the breather, real quick and then settled down at 5-6.

The Subby doesn't burn oil, only fuel.

Don't get sucked in.

Just a note incase anyone thinks ALL lycomings can run with only 2 qts.
The Lycoming Manual page 3-12B shows a minimum for my IO-360M1 as 4qts.
Pete.

Adding 6 instead of 8 quarts

David-aviator said:

My limited experience with the 0360 evolved to the same conclusion - 8 qrts at a change was a waste of 2. The engine got rid of those top 2, probably through the breather, real quick and then settled down at 5-6.

The Subby doesn't burn oil, only fuel.

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I'm about due for an oil change and had been thinking about that (adding only 6 quarts) because I have the same experience -- I seem to lose 2 quarts pretty quick and then it stabilizes. Do others do this?

Ed

edweeks said:

Do others do this?

Ed

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Ed,

I think a huge number do....I never put the full capacity in the Grumman I flew for a couple thousand hours, and only put 8 quarts in my RV the first time so I could mark the dip stick.

Paul

Oil consumption

Just to throw another data point into the mix. I find it interesting that so many of you use a quart of oil about every 8 hours. I have a new Lycoming O-360-A1A and it burns a quart every 15 hours like clockwork. Initial break-in of the engine was with Aeroshell straight mineral oil. The oil consumption seemed stabilized from the start so at 50 hours I switched to Aeroshell W100+ (Texas warm weather). Same result.

I change oil every 25 hours. I put in seven quarts and I see a gradual reduction to 6 quarts over a 15 hour period. Then I add another quart. I wonder why some of you guys use so much more.

Chris

With new superior cylinders, our fresh overhaul O-360-A1A burns one ever 8-10...

chrispratt said:

I wonder why some of you guys use so much more.

Chris

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I've always wondered why some guys use so much less...

Actually, I am happy with a quart in 8 because it is well within specs. I think there are a lot of variables involved, such as the weight and type of oil and the finish on the cylinder walls. My old O-320 in the Grumman gave me about 12 hours to the quart, and I was happy with that. It was Nitrided. I have head of chromed jugs that use more. I have Cerminil....but I don't know anyone that has done a scientific study to correlate oil usage with anything. (I just suspect thatyou'd find a correlation to cylinder finish - I have no proof of that...) Everyone seems to have their anecdotal usage, but you'd probably have to put as much work into a reasonably detailed study as you would for a Master's Thesis.

I thought I'd throw my numbers out there because I happened to have them. If anyone else has detailed records over several hundred hours as a comparison, I think it would be interesting. What I noted from my graph is how the engine broke in (went from 3 hours to the quart to about 8) pretty quickly, then danced around a bit for maybe fifty or 75 hours before settling in. Don't know why....that's what makes it interesting!

Paul

My Cherokee 180 (0360) burned a quart every 7 to 8 hrs. My Mooney 201 (IO360 A1B6D) burned a quart every 7-10 hrs. My brothers Piper Dakota (0540 Lyc) burned a quart every 7-8 hrs. Our RV9a (ECi0360 A1A) burns a quart every 9-10 hrs. What I have noticed, particularly in the Mooney, was that if I am doing many short flights or practicing IFR approaches the oil burn was closer to the low end of the range--if I am on long cross country trips it was closer higher end of the range. My guess is that with all the power ups and downs on IFR practice approaches some was going out the breather. BTW all these engines had/have compression in the mid 70s.

I used to wonder if I had done something wrong at break-in untill I talked to enough people to realize that the 7-10 hr per quart range was pretty normal.

Cheers,

db
RV9a/ECi0360/James Cowl/Catto prop--106+ hrs and a permanent smile!!!!

Just when I try to really lock down my oil consumption rate, I go get silly with the airplane (acro, acm) and then who knows how much went out the breather? I wonder if even a straight-and-level flight that encounters some chop along the way will send a measurable amount of oil out the breather.

I was also comforted to see that using a quart in 9 is quite typical. I was using more until I finally got around to installing silicone rocker cover gaskets and all the little drips and seeps stopped. That could have added up over time.

lawrence said:

i change oil at 25 hours,o-320. usualy do not add oil between changes.oil consumption rate seems to vary. from 18 to 30 hours per quart.aeroshell15/50. 500 smoh. i refill to 7 quarts at oil change.seems to use the first 1/2 quart faster then the 2nd 1/2 quart. why are these lycomings varying so much on oil consumption? must be the cylinder choke or/and cylinder finish?

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I've notice a lot of factory Lyc's seem to have lower consumption then overhauls, don't know if this applies to you or not...