Oil Consumption Data

[Ironflight]

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

[Bryan Wood]

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,

[Wes Hays]

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

[Ironflight]

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

[AlexPeterson]

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.

[osxuser]

Originally Posted by AlexPeterson

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.

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

[David-aviator]

Originally Posted by Ironflight

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

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.

[fodrv7]

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.

[edweeks]

Originally Posted by David-aviator

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.

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

[Ironflight]

Originally Posted by edweeks

Do others do this?

Ed

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