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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From their website

Decalin RunUp is approved for use with the new 100VLL (Very Low Lead) fuel announced by the FAA on Special Airworthiness Bulletin NE-11-55.  Decalin RunUp contains two types of additive, one to reduce the negative effects of tetraethyl lead in aviation fuel and the other to improve the combustion efficiency, reduce combustion deposits and clean the fuel delivery system in aircraft.  Users can expect the same level of engine cleanliness when using this fuel and Decalin RunUp as they saw with 100LL.

Decalin RunUp is not approved for use in the engines of certified aircraft but it has the same active ingredient, Tri Cresyl Phosphate as our previous product. Lycoming clone users have reported very good results when using this product.
RunUp MSDS Download Adobe Reader

Notes on using Decalin RunUp:

Some white deposits may be seen on the plugs and in the exhaust pipe during use; this is normal with RunUp since the lead in the fuel is being converted to non conductive lead phosphate. When no additive is used, lead oxide is formed. It is lead oxide which causes plugs to misfire due to its partial conductivity shorting out the plug. In addition, lead oxide tends to form in large clumps or clinkers whereas the lead phosphate is crumbly and if any is left behind in the combustion chamber it deposits in even layers.

  • Scavenges Lead in aviation fuel after combustion to prevent lead oxide buildup on valves but still allows the lead to perform the anti-knock function prior to combustion.
  • It is an excellent additive for auto conversions, where it reduces buildup on oxygen sensors and plugs. If you have to use 100LL, then this stuff is for you.
  • Prevents valve seat erosion from valve seat micro welding. It is equivalent to TCP (for experimental only).

- See more at:

Hi Wayne,

Yes I ground my fueling system to the exhaust pipe during fueling with a  clamp. The 93 Octane in Maryland has up to 10 % ethanol at almost all stations. A few ethanol-free stations in the state aren't near me. Rotax allows up to 10%, but you also have to make sure all other rubber in the fuel system will handle it. The Rotax Service Instruction, S.I. 914-019R6, talks about fuel, oil, and coolant. See 5) for the ethanol use.Under 5.2) they talk about fuel additives. I believe the TCP additive is either banned or not recommended to be carried in the plane, whereas the Decalin can be carried.

The STA-bil I use is from Walmart. I get either the one listed for ethanol or the one for marine use.

The Decalin I get at Aircraft Spruce. You can read about it there.

I add STA-bil to my drum when I re-fuel, and add Decalin to my fuel tanks when I'm forced to use 100LL.


Local I run a mix of 33% 100LL and 67% no ethanol 87 octane. With both stabil and runup. that's 25 gal 100LL to 50 gal 87 no ethanol. That gets the octane up w/o the ethanol and the runup supposedly takes care of the lead from the 100LL. We can't get 93 no ethanol here.

X-C I use 100 LL like everybody else with runup

I got an 80 Gal saddle tank off an 18 wheeler mounted to a Harbor Freight trailer with a 110AC pump.


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