Oil Change Time - How important to heat oil before draining?

[redraider]

Time for an oil change and weather is awful so I don't want to fly or run-up to heat up the oil prior to draining.  If I'm going to drain the oil for a day or two, is it critical to heat up the oil prior to draining?  I think once left to drain for a substantial amount of time, there isn't really a need to heat, but there may be some other reason, other than expediency, to heat the oil that I'm unaware of.

 

Any thoughts?

[jetdriven]

heating it makes it drain faster, but running it on the ground adds a lot of mositure and then even less will drain out because its all in the motor. I'll fly it if I was going to fly it anyways, otherwise I drain it cold and go flying after.

[RobertGary1]

I've not found that running it on the ground adds any appreciable heat to the oil. One trip around the pattern and its fully warm.  Even warm, it takes a good 20 minute to drain all that will drain. Its up to you how important it is to get the last bit out. Some people are really particular about getting as much out as possible but probably not aware that there is a lot still in the system either way.

 

-Robert

[Mooneymite]

If you've ever removed an engine sump, you know that there's a build up of goop (that's a technical term for old, congealed, dirt-laden oil    ) on the bottom of the sump that didn't flow out during oil changes.  

 

While running the engine doesn't assure that all the goop will be put into solution, I suspect that a cold oil change leaves a lot more behind.  I would further opine that the longer the engine runs prior to the oil being drained, the more of the offending goop is suspended.

 

You might delay your oil change until your next long cross-country.  Come home and immediately drain the oil (and goop).  While fresh oil is a good thing, getting the dirt out of the engine is good too.

[Piloto]

Running the engine prior to drain leaves a 1/2 qt. of old oil in the upper part of the engine. It takes at least a week for all the oil to drain down into the sump. When you mix the old remaining oil with the new one it will turn dark in about ten hours.

 

To overcome the above here is how I do it.

 

Wait at least two weeks after last shutdown.

Drain the oil into a 5 gallon container via a clear hose.

Close the drain valve.

Pour in a one gallon of AVGAS into the oil sump.

Let it stand for 15 minutes to dissolve and dilute the remaining oil residue.

Open the drain and watch the diluted remaining oil and then clear AVGAS coming out.

Close the drain after the last drop of clear AVGAS   

Fill the sump with the new oil.

 

Using the above I found the oil remains transparent enough to read the dipstick marks through it after 50 hours. It also lowers the oil consumption. Mine burns 11hrs/qt when topped to 8 qts and running at 2500rpm. I also have an M20 separator. I have been using the above procedure for over 25 years on three engines. All made it to TBO with no cylinder replacement. No need to burn your hands with a hot engine.  

 

José

[RobertGary1]

There is a total of nearly 2 quarts left in the engine/oil cooler lines, cooler, prop line, prop gov/hub, suspended that you won't get out. Don't stress about getting the last out. Old timers used to run the engine for a few seconds dry to try to pump some of it out.

 

-Robert

[redraider]

All very good points.  I hadn't heard about avgas in the sump.  Intriguing.

[jetdriven]

letting it sit two weeks before draining oil is pretty hard on it, probably less wear to do a cold start cycle and then change it.  or just fly it regularly and change it whenever you get time.

[takair]

One other consideration is if you do oil analysis. I assumed that you get more accurate results after a run since everything is suspended. Maybe a chemist has input on that.

[ArtVandelay]

If I want to do an oil analysis in between oil changes, how much oil is need to sample? Is it small enough I can extract oil through the dipstick pipe?

[RobertGary1]

If I want to do an oil analysis in between oil changes, how much oil is need to sample? Is it small enough I can extract oil through the dipstick pipe?

 

Do you not have a drain valve? Do you still have the original plug instead? Normally you just drain some off from the valve.

 

-Robert

[ArtVandelay]

Do you not have a drain valve? Do you still have the original plug instead? Normally you just drain some off from the valve.

-Robert

Because that what they recommend, otherwise you must drain a few quarts before taking the sample, I believe Avlab provides a hose in their kit to do this.

[RobertGary1]

Because that what they recommend, otherwise you must drain a few quarts before taking the sample, I believe Avlab provides a hose in their kit to do this.

 

If you are draining the oil then you just open the drain valve,let some drain out, then capture some. Its only if you do not want to drain the oil that its an issue.

 

I wouldn't spend big bucks on an aviation solution for that though. Its a common method of changing oil in the marine world (since the bottom of the oil pan would drain into the bulge), so you can probably find something reasonable at the boat shop. Some solutions use cordless drills to drive the pump that goes into the drip stick.

 

-Robert

[ArtVandelay]

If you are draining the oil then you just open the drain valve,let some drain out, then capture some. Its only if you do not want to drain the oil that its an issue.

I wouldn't spend big bucks on an aviation solution for that though. Its a common method of changing oil in the marine world (since the bottom of the oil pan would drain into the bulge), so you can probably find something reasonable at the boat shop. Some solutions use cordless drills to drive the pump that goes into the drip stick.

-Robert

I don't want to drain a couple of quarts to just get a sample, back to my original ?, how much oil is required for a sample?

I change the oil in my boat that way, but that's pulling several quarts, a bit overkill if all I need is a few drops

[RobertGary1]

I don't want to drain a couple of quarts to just get a sample, back to my original ?, how much oil is required for a sample?

I change the oil in my boat that way, but that's pulling several quarts, a bit overkill if all I need is a few drops

 

From what I've been told from Blackstone, if you pull it from the dipstick you don't need to pull any excess. Just try to reasonably put the tube such that its suspended and not sucking the bottom.

 

-Robert

[RobertGary1]

More info...

 

http://www.blackstone-labs.com/vacuum-pump.php

 

Even more...

 

http://www.blackstone-labs.com/aircraft-sampling.php

[jetdriven]

You only need about 4 ounces for a sample. I'd drain off a quart then take the sample. I couldn't bring myself to pour the quart of 25hr oil back into the engine to save 5$ so I poured it into my eagle talon to save 3$.

I did that once cold and he wear metals were consistent with a hot sample. Must be some good detergent in that oil.

[MB65E]

On the cold oil change, dump the oil wait a day with the valve open, then flush with a clean quart untill clear oil can be seen thru the drain.

Although, a quart of avgas is cheaper than a quart of oil. All in all, both do the same.

Samples... Hot oil, let it drain for a few seconds before the sample is taken.

-Matt

[Lood]

I always plan to drain the oil after a flight. I hook my home made hose up to the quick drain, open it and leave it over night. The hot oil runs out almost like water I can assure you that absolutely nothing will be coming out that quick drain by the next day, regardless of whether there is still oil, wherever in the engine or oil lines. That oil won't ever drain out in any way.

 

Interesting about flushing with Avgas, Piloto - I like the idea.

[Bob - S50]

Running the engine prior to drain leaves a 1/2 qt. of old oil in the upper part of the engine. It takes at least a week for all the oil to drain down into the sump. When you mix the old remaining oil with the new one it will turn dark in about ten hours.

 

To overcome the above here is how I do it.

 

Wait at least two weeks after last shutdown.

Drain the oil into a 5 gallon container via a clear hose.

Close the drain valve.

Pour in a one gallon of AVGAS into the oil sump.

Let it stand for 15 minutes to dissolve and dilute the remaining oil residue.

Open the drain and watch the diluted remaining oil and then clear AVGAS coming out.

Close the drain after the last drop of clear AVGAS   

Fill the sump with the new oil.

 

Using the above I found the oil remains transparent enough to read the dipstick marks through it after 50 hours. It also lowers the oil consumption. Mine burns 11hrs/qt when topped to 8 qts and running at 2500rpm. I also have an M20 separator. I have been using the above procedure for over 25 years on three engines. All made it to TBO with no cylinder replacement. No need to burn your hands with a hot engine.  

 

José

What do you do with the oil after you've drained it?  We take our drained oil to an auto parts store for recycling.  I'm pretty sure you can't do that with AVGAS in it.

 

Bob

[ArtVandelay]

What do you do with the oil after you've drained it? We take our drained oil to an auto parts store for recycling. I'm pretty sure you can't do that with AVGAS in it.

Bob

Since they refine it anyway, why not?

[RobertGary1]

The oil returned has got to be full of all kinds of stuff. Certainly a lot of anti-freeze would be in it. Not everyone is driving new cars that run perfectly. We know that a lot of gas would be in it because its one of the things that the lab tests for in an oil analysis. Granted, a quart in an oil change is a lot  but by the time its in the recovery container its probably not of any consequence.

 

-Robert

[DrBill]

I've had it take DAYS to drain cold !

[ryoder]

Should we periodically do a ten hour oil change to get more sludge out? Maybe just a quick drain and refill after a flight without changing the filter. Id lile to get to a point where my oil looks clear.

[redraider]

Thanks for all the input.  It is cold for here, KRKP, 45 degrees, and I drained the oil last night and was astonished how slow the flow was compared to hot.  A thread-like stream of oil drained as opposed to a water-like stream.  After a couple of hours I would suspect 80%-90% drained out.  I will continue to drain it for the remainder of the week as I have no flights planned.  I did take a sample after at least a quart had drained.  It will be interesting to see the results as compared to the previous "hot drain" samples. 

 

I will probably use the AVGAS method simply because I want to see if I get the same clarity as others have gotten after after a couple dozen hours of run time and I could use some lower oil consumption as well.

 

I will report any errant results.