Piper Cherokee oil usage

[jmarine225]

In my never end quest to learn more about my aircraft and the engine, I’m curious how much oil is normal to be used by the plane. Without the actual numbers in front of me, I probably have 40 or so hours since last oil change. The oil now is very dark and I seem to be adding more frequently. At this point I’m using a quart every 6-7 hours at most. There are no oil leaks and compressions are good. Curious if it’s normal to burn more as the oil gets “older” with more hours on it.

 

[idahoflier]

You're still well within spec. Lycoming says:

0.006 x BHP x 4 ÷ 7.4 = Qt./Hr

And folks on here have told me BHP is the power being produced, not data plate HP, so if you have 180 HP figure 75% or 135 HP...

https://www.lycoming.com/content/service-bulletin-no-480-f

Edit: Also, every engine seems to have a sweet spot depending on it and your normal operation. My O-360 blows out any oil over 6 QT. at high power settings..

 

[jmarine225]

Using that calculation, it seems to be almost right on at this point, and I’m adding more oil than usual, as compared to a fresh oil change. I believe it was somewhere, the older oil is, less hours per quart as it holds contaminants and more is needed in a regular basis.

 

[Jim K]

That's pretty good. The now 300 hour old engine in the club archer has settled in to using a quart every 8 hours or so. As your engine runs, the oil molecules get sheared, which reduces viscosity, and increases volatility, so oil use increasing as you near your oil change interval is to be expected.

 

[Tom-D]

In my never end quest to learn more about my aircraft and the engine, I’m curious how much oil is normal to be used by the plane. Without the actual numbers in front of me, I probably have 40 or so hours since last oil change. The oil now is very dark and I seem to be adding more frequently. At this point I’m using a quart every 6-7 hours at most. There are no oil leaks and compressions are good. Curious if it’s normal to burn more as the oil gets “older” with more hours on it.

pretty normal,, as oil gets older it uses more. The additive package is usually gone with 25 hours.

 

[Tom-D]

That's pretty good. The now 300 hour old engine in the club archer has settled in to using a quart every 8 hours or so. As your engine runs, the oil molecules get sheared, which reduces viscosity, and increases volatility, so oil use increasing as you near your oil change interval is to be expected.

explain that please.

 

[Jim K]

explain that please.

"“Shear” is described as an engine oil’s permanent loss of viscosity. This happens when the long chain polymers that maintain an oil’s viscosity at engine operating temps are broken. Shear stability is an oil’s resistance to that viscosity loss. When an oil has broken its long chain polymers and has a thinner viscosity, typical consequences are accelerated internal engine wear and higher oil consumption."

 

[Tom-D]

"“Shear” is described as an engine oil’s permanent loss of viscosity. This happens when the long chain polymers that maintain an oil’s viscosity at engine operating temps are broken. Shear stability is an oil’s resistance to that viscosity loss. When an oil has broken its long chain polymers and has a thinner viscosity, typical consequences are accelerated internal engine wear and higher oil consumption."

in plane language, the oil breaks down.

 

[RyanB]

Your numbers sound about right for that late in the cycle. Generally, 10hrs/qt is a standard consumption rate across the board, but can vary depending on a few factors. Personally, I like 40hr oil changes and have done so (+-) a few hours since I began flying the Archer but YMMV.

 

[RyanB]

Question - How fast does your oil turn color after you get it changed?

 

[jmarine225]

Your numbers sound about right for that late in the cycle. Generally, 10hrs/qt is a standard consumption rate across the board, but can vary depending on a few factors. Personally, I like 40hr oil changes and have done so (+-) a few hours since I began flying the Archer but YMMV.

Sounds good. It’s going in for the annual in three weeks so I won’t be adding too many hours before the oil change.

 

[jmarine225]

Question - How fast does your oil turn color after you get it changed?

It took a long time. My last change was in may. I’ll say in the fall it started getting darker after 20+ hours maybe? A rough guess.

 

[sourdough44]

I think the average aircraft engine turns the oil ‘dark’ much quicker that the average car. At least that has been my experience.

As to ‘burning’, we can start with how full you fill it. With an 8 quart capacity, 6-6.5 on the stick is normally what I look for. There may be slight differences in how you operate, not really sure if 100w ‘holds’ better than 20w-50.

Most any plane burns more oil than any automobile. Yes, check the Lycoming limits if concerned, as I recall, fairly high.

 

[Skip Miller]

Most any plane burns more oil than any automobile. Yes, check the Lycoming limits if concerned, as I recall, fairly high.

Auto engines (water cooled) run at thermostat controlled temperatures. Airplane engines (air cooled) run in a wider band of normal temperatures, and therefore have wider clearances designed into its bearings and cylinders. Higher oil consumption (higher than in similar water cooled engines) is normal and to be expected.

-Skip

 

[chemgeek]

Sounds pretty typical. Near the end of the last run on my O-320 it was using about 1 quart in 6 hours. My new engine, with 300+ hours, gets closer to 15, but it is slowly declining as expected. Like many engines it will "consume" more oil if filled to capacity. My sump holds 8 quarts, but I fill to 7 and don't replenish until it gets to 6. Oil consumption is quite predictable this way.

The red flags to look for are rapidly darkening oil and oil fouling on lower plugs, indicating excessive blowby. This could be early indications of cylinder or ring wear. Compressions can look good even if you are pumping oil past the rings.

 

[RyanB]

The red flags to look for are rapidly darkening oil and oil fouling on lower plugs, indicating excessive blowby.

What do you consider to be rapidly darkening oil?

 

[bluerooster]

Turning dark in oh, say about 5 hours? I go with 7 qts in the sump, and add at 6. it uses about a quart in 9 or 10 hours depending on conditions.

 

[Domenick]

If you want to truly know how much oil your engine consumes, track it.
Check oil before every flight, record tach time, hobbs time, and any added oil. Over the oil change period calculate hrs/qt. Over my last 2 oil changes the O-320-D3G in my Warrior saw 10.32 and 11.04 hours/quart.

Here is an Excel workbook with an oil tracking sheet included. Has some example entries.
https://www.dropbox.com/s/zrn2ydnw0scbxct/Flight.Logbook.Template.v2.xlsx?dl=1

 

[Arrow76R]

Phew! your post showed 10 qts/hr shocked me! Then I looked at your spreadsheet and see that you REALLY meant hours/quart!!!

 

[asicer]

Turning dark in oh, say about 5 hours? I go with 7 qts in the sump, and add at 6. it uses about a quart in 9 or 10 hours depending on conditions.

Dark after the flight? Or before the flight?

 

[WannFly]

I do oil changes every 29 tach (dont ask me why not 30, 90% of the times it has always somehow comes to 29 hours) and I burn 1 qt (+camguard) every 12 hours. its like a clockwork. incidentally my PFX headset battery also last 12 hours. so when the battery dies i know its time for oil change and vice-versa lol.

anyway, last my last oil change was at 38 hrs (flew a lot, mechanic availability issues etc) and i was burning 1 way more oil than my usual numbers.

there is a hours log in my plane, stole the format for the flight school that i maintain and have place for when i added oil, gas and hours on them.

 

[jmarine225]

If you want to truly know how much oil your engine consumes, track it.
Check oil before every flight, record tach time, hobbs time, and any added oil. Over the oil change period calculate qts/hour. Over my last 2 oil changes the O-320-D3G in my Warrior consumed 10.32 and 11.04 qts/hour.

Here is an Excel workbook with an oil tracking sheet included. Has some example entries.
https://www.dropbox.com/s/zrn2ydnw0scbxct/Flight.Logbook.Template.v2.xlsx?dl=1

I read through the spreadsheets and give you credit for the details. I am curious and confused though. It appears you only had to add 2 quarts of oil after running the engine for nearly 40 hours, which makes it approx 20 hours per quart. Is that even possible?

 

[jmarine225]

I do oil changes every 29 tach (dont ask me why not 30, 90% of the times it has always somehow comes to 29 hours) and I burn 1 qt (+camguard) every 12 hours. its like a clockwork. incidentally my PFX headset battery also last 12 hours. so when the battery dies i know its time for oil change and vice-versa lol.

anyway, last my last oil change was at 38 hrs (flew a lot, mechanic availability issues etc) and i was burning 1 way more oil than my usual numbers.

there is a hours log in my plane, stole the format for the flight school that i maintain and have place for when i added oil, gas and hours on them.

View attachment 92603

I do have something similar in the aircraft I use also. Thanks.

 

[SoCal RV Flyer]

Sounds pretty typical. Near the end of the last run on my O-320 it was using about 1 quart in 6 hours. My new engine, with 300+ hours, gets closer to 15, but it is slowly declining as expected. Like many engines it will "consume" more oil if filled to capacity. My sump holds 8 quarts, but I fill to 7 and don't replenish until it gets to 6. Oil consumption is quite predictable this way.

The sweet spot on my IO-320-D1A is similar...I try to keep it at 6 quarts, +/- about 0.2 quarts. Any more just goes to preserve the aluminum on the belly.

 

[Domenick]

I read through the spreadsheets and give you credit for the details. I am curious and confused though. It appears you only had to add 2 quarts of oil after running the engine for nearly 40 hours, which makes it approx 20 hours per quart. Is that even possible?

Not all of the last added quart was consumed, and the sump may end the period with more oil in it than it started with. For example if the engine starts at 6 quarts in the sump, and it drops to 5-3/4 and I add a quart it bumps to 6-3/4. If another quart is added at 6 or 6-1/4 then consumption was only 1-1/2 to 1-3/4.

The engine in the example ran out to 3000 hours before I replaced it.

 

[jmarine225]

I just checked the numbers according to the book in the plane. It’s due for an annual change and annual now. The last oil change was June 1. Since then I’ve been getting gradually less hours per quart. I’m now down to approximately 5.5 hours per quart after approximately 40 hours since oil change.

 

[WannFly]

I just checked the numbers according to the book in the plane. It’s due for an annual change and annual now. The last oil change was June 1. Since then I’ve been getting gradually less hours per quart. I’m now down to approximately 5.5 hours per quart after approximately 40 hours since oil change.

That’s way too much time in terms of months, at least for me and if I recall, the book says every 3 months or 50 hrs? Anyway, I follow 30 hrs or 3 months whichever is sooner. Granted i live in extreme temperatures, not sure what people in the warmer regions do.

 

[jmarine225]

That’s way too much time in terms of months, at least for me and if I recall, the book says every 3 months or 50 hrs? Anyway, I follow 30 hrs or 3 months whichever is sooner. Granted i live in extreme temperatures, not sure what people in the warmer regions do.

Well I’m in northeast pa here so I’m guessing it ca t be much worse than that. I thought the poh said 6 months or 50 hours. Again, it goes in the second week of January.

 

[WannFly]

I’m guessing it ca t be much worse than that

it does, i am in Fargo , ND

think you are correct, for spin-on filters is 50 hours, or 4 months (per service manual). from what i have gathered from oil analysis reports, as long as you are running the engine frequently and the consumption is per the book calculation as mentioned in the second post, you should be good.

 

[chemgeek]

What do you consider to be rapidly darkening oil?

I would say something like the oil turning black in 5-10 hours. Normally, my oil won't start to look really grungy until 25-30 hours or so. It's the combination that gets my attention: increasing oil consumption, decreasing time to oil turning dark, and increasing oil fouling on startup/run-up. If you can "burn off" deposits on the spark plugs during run-up, it may be a sign of mild oil fouling. When the top plugs start to get oily, too, you definitely have a problem to be investigated.

 

[jmarine225]

I would say something like the oil turning black in 5-10 hours. Normally, my oil won't start to look really grungy until 25-30 hours or so. It's the combination that gets my attention: increasing oil consumption, decreasing time to oil turning dark, and increasing oil fouling on startup/run-up. If you can "burn off" deposits on the spark plugs during run-up, it may be a sign of mild oil fouling. When the top plugs start to get oily, too, you definitely have a problem to be investigated.

Well I have the increasing consumption, and just last week I had a problem with the right mag during run up. I was able to burn it and no issues. Both mags were installed this summer. Again the ap, pulled the plugs and did compression checks approx two weeks ago and no issues. I’m guessing it’s def time for an oil change.

 

[chemgeek]

I just checked the numbers according to the book in the plane. It’s due for an annual change and annual now. The last oil change was June 1. Since then I’ve been getting gradually less hours per quart. I’m now down to approximately 5.5 hours per quart after approximately 40 hours since oil change.

Oil is cheap. Aluminum is expensive. I won't generally go past 40-50 hours or 6 months. Engines stay nice and shiny that way.

 

[chemgeek]

Well I have the increasing consumption, and just last week I had a problem with the right mag during run up. I was able to burn it and no issues. Both mags were j stalled this summer

Personally, as an owner (not a mechanic) I'd just continue monitor things and pay attention to trends. If you are in for annual at some point, pay attention to plug condition. If you start getting more frequent anomalous runups, I would ask to pull and inspect some bottom plugs and/or investigate the offending mag. That would be a case of your engine talking to you.

 

[Stephen Shore]

Oil turning black about midway through the change cycle is normal. 15 hours and you will usually start to notice it turning black and by the time you get to 40 hours it will be completely back in a normal mid time healthy engine. This is due to some normal wear on the rings.

Oil will be a chocolate brown color on a new or freshly overhauled engine. This is how you can tell if you got a good break-in.

 

[SoCal RV Flyer]

Oil will be a chocolate brown color on a new or freshly overhauled engine. This is how you can tell if you got a good break-in.

Mine's a sort of greenish brown at 40 hours...the devil's split pea soup! About 440 hours on engine.