100 LL ethanol free gas recipe

[Jerrytex]

I have 89 octane ethanol free gas available. I Need 91 octane for the 912 ULS. I am thinking of mixing 100LL and the ethanol free gas, along with decalin, to get close to 91 octane. That way I get less lead, and no Ethanol, but still get the required octane. Anyone know how much 100LL I need to add to the the 89 octane gas?

[Av8r3400]

Remember, autogas is labeled with the "AVERAGE" octane, where aviation fuel is the "MINIMUM" octane. You're better off to just use the 100LL with Decalin (and non-synthetic oil changed at 25 hour intervals) to mitigate the lead. Then you know you have good fuel.

[Flybyjim]

I agree with the 100% LL, better yet is Swift 94. I have been using 94 for the past 3 years, engine seems to run cooler and smoother. (912uls-carb)

[jrevens]

I've got a 40 gal. tank, mounted in my truck, that I fill with 91 OCT unleaded ethanol-free mo-gas from a local supplier (Sam Hill Oil Company) for my Kitfox. They also stock racing fuels (over 100 OCT). I got 35 gallons a couple of days ago for $3.54/gal. It's been absolutely trouble free for me for several years now. I usually add Sta-Bil when filling the transfer tank. My Rotax feels strong, starts well, and is flown at relatively high altitude - field elevation about 5700'. I've never found the tiniest particle in my filter or sump sample. Maybe I've just been lucky, but I feel real good about using it, especially when checking spark plugs or looking in my nice, clean oil tank.

[JoeRuscito]

I have the same issue. Only 89 available without ethanol in Charleston, SC. I do mix but not by any exact means. There’s likely always 50% 89 and 50% 100ll but I’m certain it’s occasionally swung 80/20 in both directions. Never had any issue with my 912is. When I’m running this mix it is usually the winter and not all that hot. Maybe max 85 F. I think there’s less chance of knocking in cooler temps if the octane is too low, correct me if I’m wrong. At least that’s how I justify.

I went down the finding the recipe route. The issue I found is that there’s no easy conversion between the two ways of rating octane or anti knock index. Also I believe the way lead changes the octane is non-linear.

[efwd]

If you wish to be a chemist and experiment with fuel you could always just go pick up a can of Octane Booster from the automotive supply store. It tells you on the can how much to add. I wouldn't recommend this approach myself but some are more adventurous than I. Pricey gas in the end as well.

[avidflyer]

There was a tiny little gas station near me that sold what was supposed to be 100 octane auto gas from one of his tanks. He would add Justice Brothers octane booster to the premieum auto fuel he had. He got it in 15 gallon barrels. (In Mn we can get premium auto fuel with no alcohol) He sold this stuff to the racing guys in the area. Anyway, I thought I would try some in my Avid Flyer. I had just installed a new Jabiru engine in the plane and they specify higher octane fuels for this engine. Before I started to use this stuff in my fiberglass tanks, I figured I would do some testing. I had a plastic bottle that I used to test for alcohol in gas with, it was about 1" x 6" tall. I put some small pieces of fiberglass in the bottle and filled it with the souped up gas. Next day the bottle was empty. It had softened to the point were it melted the bottom out enough for the gas to leak out. I had used this bottle plenty of times before with regular car gas with no issues. Never did find out if the souped up gas was bad for fiberglass or not. The moral of this story is: be careful of what you put into the fuel tanks. I would be far less afraid of mixed gas than I would of octane boosters. JImChuk

[Jerrytex]

Thanks all.

Since posting this , I have discovered that there are a lot of people mixing 100LL and EO pump gas with good results.

I was mainly looking to see if someone had a ratio.

I did find an octane calculator.

http://wallaceracing.com/octane-mix-calc.php

Not specifically for 100LL but from what I read on Rotax owners.com and some other flying forum sites, it seems pretty close to what I have discovered others using.

I have the newer tanks but I still refuse to run Ethanol or any alcohol boosters. I have seen firsthand what it does in and to a carburetor, way too many times for my comfort level.

I used decalin and do believe that it does pull the lead out, so that is an option.

I think the long term answer is Swift fuels getting more distribution sites, but in the meantime, I think I'll go with a 70/30 mix of E0 89 and 100LL and decalin.

[Dave S]

Some years ago, I ran into an FBO at an Iowa airport, in a town I can't remember, who serviced a whole lot of experimentals and light sports equipped with rotax 4 strokes and his formula was 25% 100LL and 75% corn free 91 octane car gas. A bit of stability and octane help without lead poisoning the rotax engines.

Personally I think sticking with known commodities and avoiding woffie juice and pixie dust is a good policy. The Iowa guy did not use any "miracle" additives.

[littlecricket]

I hoping Swift 94 becomes more prevalent in the west soon…