Perhaps this has been asked and answered, so if someone will link me to the right discussion, I'll appreciate it.

However, if any progress has been made, or if there is any new folklore or fact, please advise.

I have been told that it's ok to fuel with 91 octane auto fuel containing ethanol or with 100LL. I also have been told that there are only three places in the entire state of California where 91 octane auto fuel without ethanol can be purchased, and that it costs in the neighborhood of eight bucks a gallon.

How do you Rotax flyers handle this?



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So I've read that 91 premium is recommended, up to 10% ethanol. 100LL not advised but ok in a pinch but you need to take special precautions. Having only flown cessnas to date, I'll admit that I don't know how easy it is to find 91 gas at airports. But I think 10% is readily available on the forecourt.

This said, I'm yet to start my Rotax up so hopefully someone flying it can give proper advice.

I put 91 premium with 10% ethanol from the cheap gas station near the airport and performed flawlessly. So about $15 per hour at high power settings going 100 mph with slats off. Put about 6 gallons of 100LL once and didnt seem to run any different. I ran in 100 plus degree weather down to 33 degree and no difference.

Thanks, Christopher and Jon.


Engines prefer 91 octane automotive fuel. The real problem comes using 100LL fuel. 100LL "Lots of Lead" has 10X the lead of automotive fuel. This lead contaminates the oil and remains in suspension like grey tooth paste. Use of 100LL requires oil changes at the 25 hr interval vs. 50 hr changes on 91 octane automotive fuel. Use Aeroshel Sport Plus4 engine oil in your motor. It is a semi-synthetic with a gear box lubricant additive.

Thanks, Bob. I'm mainly worried about the ethanol.



I've been using 91 Octane auto fuel from the local service station for 400 hours now.  No problems.  I'm in AZ so I fly in very hot weather where vapor would be a problem, but have not experienced it.

The Rotax and it's gear reduction unit prefer the 91 octane like Bob said.  The lead in the LL deposits on your spark plugs, gears, etc.  If you use LL all the maintenance cycles are cut in half.  For example.  Oil changes using 91 octane are every 50 hours.  If LL is used oil changes are every 25 hours.  Same with the gear reduction unit.  FWIW

Yeah, I suspected that. How to you get the fuel from the local gas station to your aircraft, especially if you're in strange country?


I am curious then to know whether you fly everywhere with empty fuel cans so you can go off-airport and get gas, or sometimes with full fuel cans if you know you are going somewhere you can't get off-airport (or there is no airport).


Using off airport unleaded fuel wouldn't seem practical if you are flying any type of cross countries. There are 5-6 of us at Corona, CA that have Rotaxes, and none of us use auto fuel, there isn't any at our airport, and we do a lot of XCs where it would not be feasible anyway. We do use Decalin, available at AS, that's made for Rotaxes to help reduce the effects of the in the fuel. We've used it for 10 years+, it works, and the FAA approved it for 100 VLL, but I don't know if for 100LL. 

All I can say is this group regularly flies to Washington, Idaho, from CA throughout the year, and across the US to OSH and SnF, and it's done with 100LL with Decalin. Matter of fact, the only time I've had an issue with fuel was when I used auto fuel at a small airport in the midwest and it was contaminated with water and dirt because it didn't get used much.

You met Doc (Remos), has been with me flying to NYC and SnF several times, has 2,000 hrs on his Rotax 912, never used auto unleaded fuel, always 100LL with Decalin. Also, Remos issued a bulletin to Remos owners that Rotax approved Decalin being used in their certified aircraft.

For us to stop and search out unleaded and deviate just to make sure we get it would sure make XCs a pain, and a long one at that. Maybe others have come up with solution. Three of our group have Jabirus, and they also use 100LL Avgas, but I don't know if they use Decalin also. 

Walt Snyder

Thanks a bunch, Walt. At least your info makes me feel better about flying behind a high-rev Rotax.

I greatly appreciate all y'all more experienced pilots helping this ol' new kid learn about this stuff. I'm gonna look up Decalin and other additives on the Internet, so I don't have to bother all y'all with a bunch more questions . . .

Wayne Tyson

I have a 30 gallon drum mounted on a Harbor Freight Trailer with a 12V pump, I use to get 93 octane from Sams club to use in my plane . Today's price is $ 2.32 per gallon. I use this auto fuel while in the area of my home airport. When refueling away from home I can only get 100LL which I also add  Decalin to. For the 93 octane I add STA-bil to that. I think I end up using auto fuel between 50-70% of the time, so I change oil somewhere before 50 hours at a convenient time. I use Aeroshell Sport+4 oil.


Thanks, Jim. Do you ground your aircraft to the trailer? What do you think of the CO2 systems?

I'm not familiar with Decalin and STA-bil. Do they prolong storage life and reduce varnish or have any effect to counter the effects of ethanol or lead?

Does the 93 octane have ethanol? I'll see if I can find it in CA. Let us pray, in the meantime, for banning ethanol, which does not pencil out on a net-energy, cost, or "environmental" basis. One more sleight-of-hand government give-away to Agri-business.



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