Warming Engine Before Oil Change?

I know that Rotax recommends warming the engine to operating temperature before draining it, but I couldn't find an actual number listed in the maintenance manual. Is 122 degrees considered operating temperature or do I need to get the temperature up to the 180-190 range?

rdockery_3 said:

I know that Rotax recommends warming the engine to operating temperature before draining it, but I couldn't find an actual number listed in the maintenance manual. Is 122 degrees considered operating temperature or do I need to get the temperature up to the 180-190 range?

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Anything over 122 should be fine. The goal is simply to warm the oil so that it is less viscous and will drain more readily/thoroughly.

jsalley said:

Anything over 122 should be fine. The goal is simply to warm the oil so that it is less viscous and will drain more readily/thoroughly.

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And also to make sure that contaminates are suspended in the oil rather than settled on the bottom.

IMO it's a good excuse to go do a couple laps in the pattern and get it truly up to operating temp.

More warmer is more better.

I just watched a 2 hour Youtube video by Lockwood on familiarization with the Rotax family of engines. They do not recommend warming the engine first, as all the oil with its contaminants is in the reservoir with burping after the previous flight, and who wants to work on a hot engine. They do suggest frequent cleaning of the reservoir for lead deposits if burning Avgas and the use of a Decalin like product.

flightdoc101 said:

I just watched a 2 hour Youtube video by Lockwood on familiarization with the Rotax family of engines. They do not recommend warming the engine first, as all the oil with its contaminants is in the reservoir with burping after the previous flight, and who wants to work on a hot engine. They do suggest frequent cleaning of the reservoir for lead deposits if burning Avgas and the use of a Decalin like product.

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I would think you'd be leaving more old oil in the engine by not warming it though. My oil level is always lower when I burp the engine cold vs burping right after flying.

rdockery_3 said:

My oil level is always lower when I burp the engine cold vs burping right after flying.

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I felt the same way until calculating the volumetric expansion which adds about 120ml for hot oil. That equates to approximately 1/4 of the flat spot on the stick. What is also to consider is the warm oil is easier to burp.

seagull said:

I felt the same way until calculating the volumetric expansion which adds about 120ml for hot oil. That equates to approximately 1/4 of the flat spot on the stick. What is also to consider is the warm oil is easier to burp.

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If you anticipate an oil change before the next flight, "burp" the engine after the preceding flight. Then, all the oil is in the reservoir, and you can work on a cold engine.

flightdoc101 said:

If you anticipate an oil change before the next flight, "burp" the engine after the preceding flight. Then, all the oil is in the reservoir, and you can work on a cold engine.

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Not sure where to start with this, except to say that If this is how the 912 worked there would be no need for the burping process at all.

When the engine is shut down, it is essentially burped. As the engine sits oil will flow back to the crank case over time. This is the reason that the burping procedure is necessary, returning oil to the reservoir for an accurate level check.

rdockery_3 said:

I know that Rotax recommends warming the engine to operating temperature before draining it, but I couldn't find an actual number listed in the maintenance manual. Is 122 degrees considered operating temperature or do I need to get the temperature up to the 180-190 range?

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We used to immediately drain oil when something came in the shop for oil change or annual. If it’s not hot, pop the drain plug a 5pm and the next day you’re good to go. It’s just because cold oil has the consistency of Golden Eagle Syrup and takes forever to drain.

flightdoc101 said:

I just watched a 2 hour Youtube video by Lockwood on familiarization with the Rotax family of engines. They do not recommend warming the engine first, as all the oil with its contaminants is in the reservoir with burping after the previous flight, and who wants to work on a hot engine. They do suggest frequent cleaning of the reservoir for lead deposits if burning Avgas and the use of a Decalin like product.

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You should be doing compression checks on a hot/warm engine. So that’s why it makes sense to kick off annuals with oil change and compression checks. But you do need some gloves because those plugs will be hot.

D-Dubya said:

More warmer is more better.

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Yep, before every oil change - I alway go fly out to the practice area, play around for 5 min with some acro and then straight back into the hanger to decowl, dipstick out and drain the oil while its still hot. I then get the filter off and drain that too. Once everything in the pan has drained out, I'll even do the extra step of putting the tail wheel up on a sawhorse or stool to get the nose level and drain that last tiny bit out of the pan, since my drain plug is on the FWD edge of the oil pan.

I’ve done more oil changes in my 50 years of driving planes than I can count! ALL where done hot! One of my current A/C has a 912 and I never burp it as I check the oil when I’m done flying, that’s the true level when it’s operating.
Each to their own

On a full moon night, after a session of snap rolls…preferably outside…with Andre Bocelli on the CD, because everyone knows you have to have the proper oil harmonic prior to an oil change to keep the particulates in suspension…then and only then…when the resonance of the universe aligns, can you let the liquid pour from the drain.

It’s preferable to stand on one foot as you drain the oil barefoot, so as to be grounded…for earthfulness… as the oil cools you dip two fingers and make oil whiskers on your cheeks…under strong LED pen light, if your cheeks glow metallic….you are doomed for all eternity.

If you just glisten…continue.

The Oil Blessing is quite complicated and should only be attempted by those most knowledgeable few souls who can divine cam/lifter provenance and speak in the tongues of petroleum distillates and metallurgical mayhem.

Buy an extra quart….pour it….wear it….be one with the universe…Go forth with the oil…and prosper

and thou hath…aviation.

Yeah, ummmm...I know that stuff is legal in a lot of states, but you probably shouldn't be using it heavily when you're on the VAF forum. Just sayin'...

Capt said:

I’ve done more oil changes in my 50 years of driving planes than I can count! ALL where done hot! One of my current A/C has a 912 and I never burp it as I check the oil when I’m done flying, that’s the true level when it’s operating.
Each to their own

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Is it a good idea to start the engine without all of the oil being in the reservoir?

N8DAV8R said:

Not sure where to start with this, except to say that If this is how the 912 worked there would be no need for the burping process at all.

When the engine is shut down, it is essentially burped. As the engine sits oil will flow back to the crank case over time. This is the reason that the burping procedure is necessary, returning oil to the reservoir for an accurate level check.

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N8- I am not really clear why burping the engine the day before oil change, after a flight , and burping the engine warm on the day of the oil change are substantively different. The oil is definitely thinner when warm, but draining from the reservoir can be complete even if cold.

Mel said:

Is it a good idea to start the engine without all of the oil being in the reservoir?

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An engine doesn’t know it’s oil level at start up, as long as there’s enuf to supply oil at the least the min pressure then there should be no issues.
As an Eg in my Lycoming O320 I run it as low as 4 qts that’s half its sump capacity, actually Lycoming say 2 qts the min, I’d baulk at that level though!
The oil pressure in my Rotax at start comes up instantly so burping isn’t necessary in my mind.

flightdoc101 said:

N8- I am not really clear why burping the engine the day before oil change, after a flight , and burping the engine warm on the day of the oil change are substantively different. The oil is definitely thinner when warm, but draining from the reservoir can be complete even if cold.

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You have shifted a little bit from your original comment that I was responding to by adding 'day before', but the idea is the same. You may have a fundamental misunderstanding about the oil system and burping procedure. In the simplest of terms: When draining, changing, or checking the oil it is important to burp the engine at the same time you perform said procedure. A running engine is pumping oil to the reservoir, the same thing as burping.

The purpose of burping the engine is return oil to the reservoir. While the engine sits oil will siphon back to the crankcase. That oil needs to be in the reservoir in order to measure or drain it. I'm not going to entertain the discussion on how fast that happens and how many hours or days it takes for a meaningful amount to flow because it really doesn't matter, the best practice is to do this immediately before the procedure.

This should not be confused by the oil checking process that Capt is describing and that you may have heard via hangar talk or videos. In that case, at the end of a flight the engine has been running and pumping oil. It will be hot and in the reservoir. This is a good time to get a valid oil check. Although, In this exact same scenario when you come back day(s) later, oil will have returned to the crankcase and would no longer be in reservoir for valid checking or draining. As Capt and Mel are discussing for a separate reason (start up), oil in the crank may or may not be less available to bring up pressure. I'm not taking any position in that. We do the oil check before we fly, because I share an airplane with my daughter who is a student pilot. Student pilots follow the POH. Also, since there are multiple users you aren't always the person who checked it after the last flight. This means checking before you go.

Honestly you can check it or drain it as warm or cold as you want to and after one flight or before the next and you'll be ok. Those details are secondary to just making sure you pump from the crank to the reservoir via burping or running at the same time you are doing it.

Capt said:

An engine doesn’t know it’s oil level at start up, as long as there’s enuf to supply oil at the least the min pressure then there should be no issues.
As an Eg in my Lycoming O320 I run it as low as 4 qts that’s half its sump capacity, actually Lycoming say 2 qts the min, I’d baulk at that level though!
The oil pressure in my Rotax at start comes up instantly so burping isn’t necessary in my mind.

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Apples to Oranges. The Lycoming is a wet sump engine. The Rotax is a dry sump. The Rotax oil pump does not pick up oil from the crankcase.
Is it possible for enough oil to drain into the crankcase that there may not be enough left in the reservoir? I don't know. Just asking.

Personally if I'm running a dry sump engine, I want all possible oil in the reservoir during startup.