New wing tanks

[Vande17941]

Are the new tanks from kitfox compatible with unleaded fuels that may contain ethanol? (california&#128547. Any issues with new tanks that I need to be aware of?

[GuppyWN]

They are “ethanol resistant.” Kitfox recommendation is 100LL w/decalin. I run 91 ethanol free in my 912ULS.

[Vande17941]

What does this mean "resistant"? If that is the case, why are they recommending 100LL? Obviously I would like to use mogas because it's a 912. So what's the real truth of what the tanks can handle?

[GuppyWN]

You’d have to ask the factory but I think the answer is even they aren’t sure. If you have iOS you can download an app called Pure Gas and it will help you locate ethanol free gas. I quality control check by partially filling a small jar with gas and putting a single drop of food coloring in and shaking it. If it’s ethanol free the food coloring will remain solid and balled up. If it’s got ethanol in it the food coloring will look diluted.

[JamesD]

I have a 2000 model skystar series 5. here in Australia they do not sell ethanol gas without stating. my tanks have been dry for 6-7 years due to being ground looped then i purchased it. they look very good and i am confident they with be fine and most likely would of had only 100LL over their 750hrs in use. should i be concerned as i am currently re bagging the wings but changing the tanks is one hell of a job for nothing.

[Av8r_Sed]

My early 90’s vintage Denny Aerocraft tanks have only seen ethanol free and 100LL. They’re fine and I’ve had no trouble with them. Even the Kreem sloshing is in good shape. I wouldn’t be concerned with yours. Might want to check them for leaks though before you (re)cover the wings.

[Auster]

I have a 2000 model skystar series 5. here in Australia they do not sell ethanol gas without stating. my tanks have been dry for 6-7 years due to being ground looped then i purchased it. they look very good and i am confident they with be fine and most likely would of had only 100LL over their 750hrs in use. should i be concerned as i am currently re bagging the wings but changing the tanks is one hell of a job for nothing.

James this is not a definitive answer, just a sharing of experience. My Skystar S5 is about the same vintage as yours, first flying in 2007. It now has nearly 500 hours, 90% of which has been on 95 or 98 octane Mogas. Much of that had 5% ethanol. The remaining hours were on 100 LL avgas, when I could not obtain mogas. I am in Europe and we have very good quality fuel delivered to our airfield. Only rarely, on trips, have I used fuel from a local garage.

After reading of issues with earlier model Kitfox fuel tanks I've decided to do an annual check on the tanks - which were treated with Kreem as part of the build process. At the last inspection we drained them completely, including removing the fuel drains. No dirt or contamination was found. We then used torches to visually check the security of the Kreem. It is in good condition except for some cracks where the baffles join the skin - that right angle join - a known problem area on early Kitfoxes. While a little concerned about the cracks we decided that this was not yet causing any issues e.g. no flaking of the Kreem or leaking. We also decided to continue this annual inspection.

In your case I would proceed but keep a close eye on the security of the Kreem at the baffle joints and, as far as possible, avoid ethanol, but keep in mind that fuel without ethanol might be difficult to obtain in the future.

[jiott]

Regarding tank coatings, the older Kreem types or even newer stuff, I have seen way too many reports in these forums over the last 6 years I have participated of folks having serious problems with it flaking off and seriously plugging screens and filters. Mind you there are also many that swear by the stuff. To me it is too high of a risk of catastrophic engine starvation. If my uncoated new style ethanol "resistant" tanks SLOWLY over the years start to soften and even spring a slow leak, I think that would not be catastrophic and most likely would give plenty of prior warning-a much better risk situation in my mind. I would stay totally away from any kind of coatings in the newer tanks.

[jiott]

Good question Lowell, my understanding of Decalin is that it actually alters the chemical composition of TEL when it is burned so that the residue (not 100% but a lot) is able to be blown out the exhaust rather than forming lead deposits on valves and piston rings. There are more in-depth discussions of this in the forum. Again, my opinion only, but the additive in Aeroshell Sport Plus 4 keeps the TEL in suspension in the oil that has been contaminated with UNburned fuel. All engines have a certain amount of unburned fuel that sneaks past the piston rings and into the crankcase oil. Therefore I would think that if you burn 100LL you would want to use both Decalin AND an oil with that additive. The Rotax gearboxes are very susceptible to lead deposits from the contaminated oil.

[jiott]

The new tanks do fine with ethanol free Mogas; I have been running nearly 100% clear Mogas for 750+ hours with no problems at all. I can't speak to Mogas with ethanol because I have not run it.

My understanding of Kitfox factory recommending 100LL is not because of the tanks or fuel system compatibility, but is their belief that Mogas can be dirty, unknown additives, possible water, potential vapor lock, limited availability, and possibly other reasons. I usually run my Mogas thru a filtering funnel and have NEVER seen any water or dirt in my fuel samples. I personally (and Rotax factory seems to agree) believe the very small risks of using Mogas is not nearly as bad as the detrimental effects of lead sludge and deposits from 100LL, even with Decalin. I personally know several others, and there are many more on this forum, that run Mogas nearly exclusively for many years with no problems. Most of us do try to get Mogas without ethanol.