Purge engine at oil change

[rvbuilder2002]

Originally Posted by Rick_A

When I attended the Rotax class at Lockwood they said just the opposite, if you run 100LL. They showed pictures of lead sludge in oil tanks after just 25 hours of running 100LL. There was more than 1/4" of lead sludge in the bottom of the tank.

Their message was: When using 100LL change the oil at 25 hours and clean the oil tank. If you run auto gas, change the oil at 50 hours and you don't need to clean the tank.

I was taught the same, and have also observed the same.

[RFSchaller]

It's possible the instructor was referring to engines run on unleaded auto gas. He was definitely a proponent of unleaded gas.

[f1rocket]

I have run for periods of time on both types of fuel. Around home, I burn premium unleaded Shell 93 octane with up to 10% ethanol. When I fly cross country, I burn 100 LL with Decalin added.

There is definitely a film in the oil canister if I use much 100 LL. I can also see it in the oil as it tends to darken more quickly on 100 LL. I go 50 hours between oil changes if it is mostly auto fuel, and shoot for between 25 and 50 if it's a mix.

Bottom line, if you burn any 100 LL, I would clean the tank at oil change.

[Sink]

Here is a copy and paste from the Rotax forum. It is an eye opener for some. I guess I'll have to put these videos in my own file. This has all kinds of implications to this engine.
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Perfect timing here for some videos.
Here is what happens when oil is left too long and the wrong type oil is used. The 912ULS engine is a 2008 with 83 hours TTSN.

You're going to love this. hmy:inch:

https://youtu.be/gxUWvlAPYZk

https://youtu.be/DrjW3rnERGA

https://youtu.be/ioGzg1KPBUw

[JBPILOT]

"A picture - - - - - - "

Thanks

[RFSchaller]

Excellent video, Joe! Thanks to Roger for making it.

[jnmeade]

Roger,
What oil was used?
Was Decalin used in this engine?
This engine has 83 hours since 2008? - 83 hours in 7 years? When was the last time it was run before the oil change?
If the engine has 83 hours on it and report is the oil was run too long on 100LL, then it must have had the oil changed once - surely it didn't have the wrong oil put in from the factory or dealer, so assuming an oil change at 25 hours, that leaves 83-25=53 hours, just marginally longer than Rotax's allowable (granted, not prefered) oil change time.
Bad oil for 53 hours over what period of time? When was the oil changed the first time? I'm trying to figure out if this engine sat with bad oil for a log time or if it ran bad oil for only a short time?
It is useful for all of us Rotax operators to know the full extent of the operating conditions in the videos. Rather than ask Roger a zillion questions, maybe Roger would just post the history of the engine in as much detail as he has and we can all share in the information and knowledge.

[RFSchaller]

Good points, Jim, but the video is still a valuable warning of what can happen from neglect.

Rich

[jnmeade]

I looked on the Rotax Owners site and didn't see it. Can anyone give me a URL to look for? TIA

[Piper J3]

http://www.rotax-owner.com/en/rotax-...hange-question