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Oil Change Interval Question

I have typically changed oil AND filter around every 25-30 hours on my IO-520BB. My mechanic at annual recommended I change oil every 25 hours, and filter every 50 -thus change filter every other oil change. He is a big proponent of keeping fresh / clean oil in the engine. Historically we have cut open filter to inspect and send off oil for analysis and everything looks healthy. I like the idea of doing this 25/50 but curious on using the filter all the way to "TBO". Happy Thanksgiving everyone!

Model: Bonanza F33A
Aircraft Serial Number: CE-628
Posted 11/22/2023 - 3 months ago
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Replies Sort

I would suggest replacing the filter every time you change oil. This way you can see any issues with the filter and take corrective actions.

Bob Ripley
ABS Technical Advisor

Posted 11/22/2023 - 3 months ago
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With spin on oil filter, change oil and filter every 50 hours or six months, whichever comes first. Cut open, spread out and examine filter media. With screen, oil change, inspect and clean screen every 25 hours or six months, whichever comes first. Oil analysis at least once per year.

Posted 11/22/2023 - 3 months ago
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Continentals M-0 Standard Practices Manual Para. 3-2: Refer to the engine maintenance manual and/or the aircraft manufacturer’s or Supplemental Type Certificate (STC) holder’s AFM/POH for oil specifications, specified oil change intervals and inspection procedures. Oil change intervals published in this manual are minimum requirements.

Continental believes more frequent oil and filter changes enhance engine service life. Drain and replenish engine oil every 25 hours of operation or 4 months for engines that incorporate a reusable oil screen. On engines with the full flow oil filters, large or small replaceable oil filter cartridge, change the oil and filter every 50 hours and/or 4 months. Inspect oil screens and oil filter elements for contaminates at each oil change. Oil analysis may be used in addition to the oil screen or filter element inspection, but not as a replacement for it.

It has been a common opinion in some circles that oil analysis should be done at each oil change. The two major oil analysis companies base their analysis on oil changes being done at 30 hours so more hours on the oil sample will skew the analysis.

Jim
ABS Technical Advisor
BPPP Instructor & Ambassador
CFII/MEI, A&P/I-A

Posted 11/22/2023 - 3 months ago
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Approved by Bob Ripley
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This is what I have been doing with my E-225-8 V Tail engine and also my Luscombe airplane that has a Lycoming O235-C2C engine. I do not expect anyone to agree with my methods but so far it has worked for me for 45+ years. As I have written a number of times both of those engines are such that a shop vacuum sucking on the breather discharge with the oil filler port open will remove that which causes the corrosion inside the engine. MOISTURE!! Purging the crankcase of that moisture after flying is what I believe lengthens the time between oil changes. I change oil between 50 and 60 hours of engine operation regardless of calendar time. Sometimes it is 6 to 8 months between oil change, occasionally more, but rarely less than 5+ months. All indications are that I have no internal engine corrosion. Those two engines are set up so a complete sweep of the crankcase with fresh air using the shop vacuum is accomplished which rids the crankcase of some very high percentage of the moisture laden gasses in there at engine shutdown. IO 520/550 engines can not be ventilated as described above. Some O-470 can be ventilated with a shop vacuum.

Regards, Lew Gage

Posted 11/23/2023 - 3 months ago
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While vacating the engine case of moist atmosphere is useful (if your engine can support this procedure and most 520/550 engines easily cannot), or having a dehumidifier hooked up to the engine… that’s not the only challenge. Inactivity and oil contaminants are the bigger factors of oil degradation, valve guide problems, corrosion & reduced engine life. Monitoring is essential but oil & filters are definitely cheaper than repairing engines (op only). Continental oil change interval recommendations are known, but here are comments from some of the others in the business. Do what you will, your mileage may vary.

Aeroshell
The primary purpose for changing oil is to remove contaminants. Low usage aircraft should have their oil changed every four months. When an aircraft engine sits idle, the used oil in the engine can be quite acidic which, when combined with water from the atmosphere, causes corrosion. This problem is then compounded when the rust particles that are formed, get into the oil and act like a grinding paste when the engine is next started, causing further wear and damage. By changing the oil more frequently, you reduce the chances of corrosion occurring resulting in a significantly less abrasive oil in the engine.

Blackstone Labs
“If you want to run longer on the oil despite having high wear, that’s totally fine. Keep your own situation in mind and make your informed decision based on what’s showing up in the oil and filter/screen (at oil analysis), what the engine monitors are telling you, and your own comfort level. It’s your airplane and your money!

When we suspect corrosion (from inactivity), we almost always recommend cutting back to a shorter oil change. While changing the oil more often doesn’t prevent corrosion from happening, it does allow you to 1) monitor the corrosion to make sure it’s not getting out of hand, and 2) get the metal-laden oil out of the system sooner, so not as much metal gets washed into the oil when you crank over the engine. Abrasive oil causes more wear.

Contaminants
Water can enter the system just from condensation in the air, though we don’t usually see more than a trace from that. When we’re consistently seeing more water than normal, we’ll often recommend going to a shorter oil change.

Fuel
If we’re seeing a lot of fuel from sample to sample, it can be a sign of something else going on so we would likely recommend a shorter oil change until you can figure out what’s up.

Environment
Where you fly (and how often) also affects how often you need to change your oil. Inactive engines in a dry place like Arizona (& Nevada) can usually get away with keeping the oil in place longer than someone in Michigan or North Carolina.

So, if we can say with good certainty that the oil itself won’t go bad just sitting in an engine, you might wonder why it needs to be changed at all? The answer to that is contamination. Engine oil has maybe the hardest life of any oil application out there. Not only does it see frequent temperature swings of 150° to 200°F (65° to 93°C), but it will also get contaminated with fuel blow-by and a little atmospheric water as well. Ideally the fuel and water will boil out once the oil gets up to operating temperature, but that contamination will add up over time and eventually cause the oil to start to oxidize.

Summary
If you can pinpoint exactly when the oil will oxidize enough that it will start to affect wear or cause the oil’s viscosity to change, (and if you don’t want to follow the manufacturer’s recommendations) that’s the point at which you want to change the oil. If that exact point cannot be pinpointed, then maybe more frequent oil changes would serve better. As Blackstone Labs says: “It’s your airplane and your money!”

Jim
ABS Technical Advisor
BPPP Instructor & Ambassador
CFII/MEI, A&P/I-A

Posted 11/24/2023 - 3 months ago
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In reply to: James Brendel | 11/24/2023 - 3 months ago

While vacating the engine case of moist atmosphere is useful (if your engine can support this procedure and most 520/550 engines easily cannot), or having a dehumidifier hooked up to the engine… that’s not the only challenge. Inactivity and oil contaminants are the bigger factors of oil degradation, valve guide problems, corrosion & reduced engine life. Monitoring is essential but oil & filters are definitely cheaper than repairing engines (op only). Continental oil change interval recommendations are known, but here are comments from some of the others in the business. Do what you will, your mileage may vary.

Aeroshell
The primary purpose for changing oil is to remove contaminants. Low usage aircraft should have their oil changed every four months. When an aircraft engine sits idle, the used oil in the engine can be quite acidic which, when combined with water from the atmosphere, causes corrosion. This problem is then compounded when the rust particles that are formed, get into the oil and act like a grinding paste when the engine is next started, causing further wear and damage. By changing the oil more frequently, you reduce the chances of corrosion occurring resulting in a significantly less abrasive oil in the engine.

Blackstone Labs
“If you want to run longer on the oil despite having high wear, that’s totally fine. Keep your own situation in mind and make your informed decision based on what’s showing up in the oil and filter/screen (at oil analysis), what the engine monitors are telling you, and your own comfort level. It’s your airplane and your money!

When we suspect corrosion (from inactivity), we almost always recommend cutting back to a shorter oil change. While changing the oil more often doesn’t prevent corrosion from happening, it does allow you to 1) monitor the corrosion to make sure it’s not getting out of hand, and 2) get the metal-laden oil out of the system sooner, so not as much metal gets washed into the oil when you crank over the engine. Abrasive oil causes more wear.

Contaminants
Water can enter the system just from condensation in the air, though we don’t usually see more than a trace from that. When we’re consistently seeing more water than normal, we’ll often recommend going to a shorter oil change.

Fuel
If we’re seeing a lot of fuel from sample to sample, it can be a sign of something else going on so we would likely recommend a shorter oil change until you can figure out what’s up.

Environment
Where you fly (and how often) also affects how often you need to change your oil. Inactive engines in a dry place like Arizona (& Nevada) can usually get away with keeping the oil in place longer than someone in Michigan or North Carolina.

So, if we can say with good certainty that the oil itself won’t go bad just sitting in an engine, you might wonder why it needs to be changed at all? The answer to that is contamination. Engine oil has maybe the hardest life of any oil application out there. Not only does it see frequent temperature swings of 150° to 200°F (65° to 93°C), but it will also get contaminated with fuel blow-by and a little atmospheric water as well. Ideally the fuel and water will boil out once the oil gets up to operating temperature, but that contamination will add up over time and eventually cause the oil to start to oxidize.

Summary
If you can pinpoint exactly when the oil will oxidize enough that it will start to affect wear or cause the oil’s viscosity to change, (and if you don’t want to follow the manufacturer’s recommendations) that’s the point at which you want to change the oil. If that exact point cannot be pinpointed, then maybe more frequent oil changes would serve better. As Blackstone Labs says: “It’s your airplane and your money!”

Jim
ABS Technical Advisor
BPPP Instructor & Ambassador
CFII/MEI, A&P/I-A

I have been exposed to a number of engine operations that very few other people have. Running autos on butane and propane with 75,000 mile oil changes and there was only a bypass 1 quart a minute filter on the engine (1949 Ford V8) Then another 74,900 miles to the next oil change. That engine showed almost NO SIGNS of wear when overhauled to go into my "WOODIE" 18 foot inboard boat some 68 years ago. Evacuating the E series engine crankcase after flying is something that very few people can do or do with their aircraft engine. So the manufacturer devises methods of operation that fit the usual treatment of said engines. The addition of a full flow oil filter also helps keep thing clean. Also, all of my aircraft engines operate on unleaded auto fuel so lead contamination is not in the picture. I said I expected most or all people to not agree with what I do but then I do not do what most people hold onto. As most E operators know, I believe I probably was the first (that I know of) person to develop a full flow oil filter system for the E series engine because I was not happy doing what everyone else was doing using a screen to keep damaging particles out of the engine bearing system

Regards, Lew Gage

Posted 11/26/2023 - 3 months ago
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Oil Change Interval Question