Long Term use of AVGAS in a 582 (any issues)?

[LSaupe]

One of the guys in our EAA Chapter would like to do some cross country flying and is using a 582. The area will not have much, if any, access to mogas. AVGAS will be primary fuel source.

He has concerns over excessive carbon buildup and lead deposits etc. Do any of you run AVGAS on a regular basis in your two strokes and what have you realized as far as performance and carbon issues?

[SkySteve]

Decalin. Buy a bottle from Kitfox Aircraft or Spruce. About $20 or so. Lasts a long time and takes the lead out of 100LL. Just pour in the right amount in your fuel tank, then fill with 100LL. I always use it when I travel out of my local area.

[KFfan]

Question,
What, if any, is the effect when refueling and mixing 100LL with Decalin and MOGAS with, or without ethanol?

[SkySteve]

As I understand it (I'm no expert), Decalin eats or dissolves the lead in avgas, thus eliminating the lead build up in the engine. Therefore, if you mix it with fuel that has no lead there would be no effect other than the added expense of using the Decalin when it is not needed.

[jiott]

My understanding about Decalin is that it does not eat the lead but keeps it in suspension and does not allow it to settle out within the engine. It stays in the fuel and blows out the exhaust after the combustion process. That is why 100LL users with Decalin will find the inside of their exhaust system slowly becoming coated with "solder".

[Danzer1]

Decalin converts lead to lead phosphate which is a powder you can wipe off. Without Decalin the lead in 100LL converts to lead oxide during combustion - which is hard as a rock!

I have never heard of anyone suffering "solder" like buildup using Decalin - any references?

[DesertFox4]

Over 900 hours of only 100 LL use with Decalin and zero build up of anything unusual in the exhaust system. On oil changes I do find a small amount of really fine lead particles in the very bottom of the oil sump but a quick wipe with a paper towel and the bottom of the can is clean again. No spark plug fouling ever either. Engine runs as new.
No idea what the inside of the combustion chambers look like but suspect very little accumulation as again the engine performs as new. I have had the gear box off twice for re-shimming in the mentioned 900 hour period and saw no accumulation there either time. This a 912 uls 100 hp. Rotax.

My model 3 with a 912 80 hp. also saw the same results after 1,100 hours of 100LL with Decalin use.

[jiott]

My reference to "solder" build-up in the exhaust came from someone who had to open up his muffler to do some welding repair. He had been using 100LL and Decalin for some time with no problems, but noticed this coating inside the muffler. I agree, I have never heard of any problems because of it, and maybe this one instance is all there is. It does sort of make some sense because Decalin does not claim their product converts ALL the lead to lead phosphate, so some lead escapes and may collect in the muffler. Anyway, apparently nothing to worry about.
I believe the "solder" incident was reported in either this forum or Van's Airforce forum, but I can't locate it now. Maybe someone else remembers it?

[napierm]

One of the guys in our EAA Chapter would like to do some cross country flying and is using a 582. The area will not have much, if any, access to mogas. AVGAS will be primary fuel source.

He has concerns over excessive carbon buildup and lead deposits etc. Do any of you run AVGAS on a regular basis in your two strokes and what have you realized as far as performance and carbon issues?

I've had a 582 quit on take off because of avgas. Had maybe 30 hours because of long cross country. Top of piston, inside of head, entire exhaust looked like it was powder coated white. Rings stuck, cylinders scored. Rotax shop knew exactly what I was talking about. No idea why there isn't a warning in service letters.

Decalin may help but I would avoid if possible.

Mark Napier

[Danzer1]

No idea why there isn't a warning in service letters.

It is in the operating manual, page 10-8. "Due to its high lead content AVGAS forms increased lead deposits in the combustion chamber and lead sediments in the oil system. Therefore use AVGAS only if you encounter problems with vapour lock or if the other fuel types are not available."

Having said that, I'm glad you came out unscathed! I don't think the Rotax warning as printed, is sufficient. Engines running 100LL need to be operated differently, and that usually is never covered.

To burn off the lead oxide, the engine needs to be run at higher than idle speeds and shut down from a higher speed. Lead oxide builds up more and faster at lower temperatures.

Running rich exacerbates the buildup.

Higher temp plugs are also wise.

Mixing 100LL and auto fuel makes the problem much worse - you should only use one or the other. Auto fuel adds reactants that promote (help) 100LL build deposits.

Personally, I wouldn't use 100LL in any water cooled engine (with or without Decalin) - they generally don't run hot enough to effectively burn off the lead oxide (change it to lead bromide). IMHO

[Flying Felix]

Do you have non ethanol gasoline available to you?

I use that in my KF2 all the time and keep about 40 gallons in the hanger ready to go.

I attached a page from my O & M manual for my engine. It is not a Rotax engine, nevertheless is good information that applies to similar engines. I underlined what it says about leaded gasoline.

They also talk about gasoline with alcohol. I traps water if you let it sit. If you fly all the time that is not an issue. Just make sure your hoses, gaskets and sealants are rated for alcohol since alcohols are very aggressive solvents.

Happy flying!

Flying Felix