For those engines that require auto gas from the local off-airport "service" station, here in California the spectre of ethanol rears its ugly head. The Internet runneth over with conflicting advice. For example, here's an infomercial (despite protestations to the contrary) for the VP Power line of products.

Is there a fuel/engine expert in the house that can provide the last word on how to and how not to fuel a Rotax?

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If the rest of your system will tolerate it, Rotax does not care about ethanol. 

You can also run 100LL with more frequent oil changes.

You can also mix the two.

Source: forum (great resource, forum is free, maintnenance videos require membership)

And therein is the key, the rest of the system, at the airport I fly out of, there sits a beautifully built kit plane, fabric covered with rotax power, variable pitch propeller, full dual glass panel. Obviously constructed to the highest standard. The kit is supplied with some form of plastic fuel tanks.... 

The owner has struggled for over a year with the fuel system on the engine, unbeknownst to him the ethanol in the fuel was slowly eating the inside of the tanks, just enough to create some loss of power, rough running, hard starting etc. Not enough to plug the filters or be obvious as to the cause, he tells me the cost to determine and correct the issue has been in the thousands!! not including a lost year of flying the plane he so lovingly created..

Education costs money, hopefully by asking and sharing we can reduce that cost.

Sorry, Michael, that post was in response to Ken.

Does anyone know if any of the additives that are supposed to be protective against the ravages of ethanol (required in CA) actually do so? (e.g., see: )


Thanks for the input. Yes, I have heard those things, including a vague reference to a "study," apparently un-referenced, that found a 50/50 combination was best. But that's my reason for hoping for something more specific firmly grounded in actual research.

Maybe I should have been more specific. I believe the three comments that I mentioned in previous post are in line with official Rotax operating specifications, not just "forum talk." Add to those three the need for minimum 91 Octane.

Yeah, Ken, but I'm an cantankerous old crank, and want to know the basis for conclusions. What did you think of the stuff Leno was hawking?


I have no basis for an opinion on VP products, but it doesn't seem like a good idea to depend on any additive to protect an aircraft fuel system from ethanol. When burning ethanol, it seems to me that what's important is that the entire fuel system (tanks, hoses, filters, valves, transducers--everything) be ethanol tolerant.  We know that the Rotax supplied portion is ethanol tolerant because Rotax tells us so.

I'd have to look it up to be sure, but I seem to remember something about Rotax being made for auto fuel without ethanol.

Not that I don't believe Rotax; I'd just like to know just what it is about the Rotax components that makes them resistant to ethanol. I'd also like to know what makes the fuel tanks, lines, and connections resistant. I'd also like to know just what "resistant" means. "Resistant" is a weasel-word commonly used in advertising.


VP is an excellent octane booster, we have run it for years in our rotax powered snowmobiles, motorcycles, watercraft and quads, whenever we cannot get a good quality fuel we would use the VP octane booster.

As for the rotax and ethanol, we have had that "stuff" here in Canada for a long time, most fuel is at least 10% ethanol, some brands are more, so rotax has been building to automotive fuel standards and subjecting their engines to ethanol for a long time, keep in mind I don't have rotax airplane engine experience, but I would doubt they would build the plane engines to a lesser standard than all the other, and they are built to last!!  

As for resistant.. here in Canada most all fuel line is ethanol resistant, at least in the four western provinces, just because we cannot buy auto fuel without some amount of ethanol.


I believe that ethanol is a directly and indirectly subsidized bit of agro-corporate welfare that could not stand on its own, nor pencil out as a net-positive from an environmental standpoint. I believe we've (the taxpayers) been sold a bill of goods, and my fellow "environmentalists" have played into the parasitical ethanol industry's hands. Much better to make good whisky out of corn.


Here in CA, there are zero suppliers of ethanol-free, unleaded 91+octane auto fuel.

I don't remember where I saw the testimony, but I read on the Internut that some A&P's had run some tests on it, unleaded with 10 percent ethanol, 100LL, and a 50/50 blend. Then they tore down the engines and found that the 50/50 blend caused the least damage. It left a powder-like coating of lead rather than solid deposits.



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