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Ethanol-containing gas in a two-stroke engine - what to do?
September 17, 2012 7:13 AM   Subscribe

What to do with ethanol-containing gas in a two-stroke engine?

I have an aircraft (a powered parachute) with a Rotax 2-stroke engine. Unfortunately, 2-stroke engines and gas that contains ethanol don't get along very well... but you can't buy E0 gas in my state.

Are products like this snake oil, or do they really work? If they don't, what are my options?
posted by dmd to Sports, Hobbies, & Recreation (13 answers total)
 
That stuff probably won't work.

E10 should be fine, however. If not, you need to buy racing gas or aviation gas.
posted by gjc at 7:22 AM on September 17, 2012


It appears that Rotax recommends an ethanol content of no more than 5%. That's going to be very hard (impossible?) to find at a regular gas station. Your best bet might be to visit a local small airport and see if you can't purchase a can or two of avgas.
posted by Thorzdad at 7:30 AM on September 17, 2012 [1 favorite]


The issue is that gas with alcohol in it will pull moisture out of the air and that will encourage corrosion. The problem is that the vast majority of engines are 4 stroke and most solutions to the problem of water in gasoline problem involve adding alcohol to encourage the water to dissolve in the gas, thereby making 4 stroke engines happy.

If you absolutely had to DIY this you could probably dry your gas with calcium chloride (or even pull the ethanol out of E10 with an aqueous extraction, then dry it) but Throzdad's suggestion is much simpler.
posted by Kid Charlemagne at 8:03 AM on September 17, 2012


It's not just moisture. Ethanol is also very hard on many seal and hose materials. Not all engines are specifically vulnerable, but many are.

Drying gas/ethanol isn't really practical either. I've tried to do exactly this in the lab with packed column cleanup. It's only marginally successful, in my view, and temporary.
posted by bonehead at 8:29 AM on September 17, 2012


You can buy VP or other brands of racing fuel in 5, 10 and 50 gallon drums at any race shop.

Get the stuff closest to pump gas and then add to pump gas to reduce the alcohol ratio to what you need. Racing gas is EXPENSIVE. Run just that if you wish but do the admixture trick to reduce the alcohol. I do it in vintage motorcycle engines which, while mostly 4 stroke, were made long before alcohol came along.

You can even get LEADED gas if you need that but your Rotax almost certainly doesn't want lead, having no valves and all.
posted by BrooksCooper at 8:33 AM on September 17, 2012


Ethanol also does really bad things to fuel lubricity too, which is the main reason it should be avoided for two strokes.
posted by bonehead at 8:34 AM on September 17, 2012


or even pull the ethanol out of E10 with an aqueous extraction, then dry it

I'm not sure that would work, the alcohol allows the water to mix (or dissolve, I forget) with the gasoline. You'd need to distill off the gasoline, or do a chemical extraction somehow.
posted by gjc at 8:58 AM on September 17, 2012


2-stroke engines and gas that contains ethanol don't get along very well

This is news to me. Everybody I know with a 2-stroke lawn mower or other power equipment (which is most people; this being a state where lawnmowers are still allowed to have 2-stroke engines) uses regular old E10 highway gasoline.

The only possible exception would be people way out in the countryside where you can get E0 "farm use" gas. But that would just be convenience if you happen to have it around, nobody drives out there for it just for a lawn mower or other 2-stroke machine.

Why don't you call up Rotax and ask them what they recommend? This article suggests using 100LL if you can't or don't want to use E10, although I'd certainly want to test it extensively if I were going to depend on it in anything approaching a life-safety application. And some airports that cater to ultralights and other small planes have "mogas" (unleaded, E0, automobile-type gasoline)... you might call around and see if that's the case in your area. Airports are exempt from the regulations about ethanol content, so even if E10 is mandated for cars, you may be able to get E0 there.
posted by Kadin2048 at 9:12 AM on September 17, 2012


Sta-Bil makes great fuel stabilizers that may help your problems. I use it in my gas tank when I store my bike for the winter.
posted by JJ86 at 9:17 AM on September 17, 2012


I learned growing up that the trick for this (at least, when it came to string trimmers and other two-strokes like that) was to use Coleman camp fuel (adding oil, of course). If you don't have access to E0 fuel, that'd be one way to go.
posted by CrystalDave at 10:39 AM on September 17, 2012


CrystalDave may be on to something there. "White gas" camp fuel (which is most commonly found under the Coleman brand, at least around here) is just gasoline with no additives. It comes in one gallon metal cans at most outdoor stores. I don't know though what its octane rating would be or if the lack of detergents and such would harm your engine. Might be worth looking into though.
posted by Scientist at 2:34 PM on September 17, 2012


Ahh, I checked up on that (as I should've before posting that comment) and at least according to Wikipedia Coleman camp fuel only has an octane rating of 50-55 and probably isn't going to be something that you want to use in an aircraft engine. So maybe don't do that.
posted by Scientist at 2:37 PM on September 17, 2012


Yeah, camp fuel is naptha (lighter fluid/ charcoal starter), not gasoline.
posted by gjc at 7:09 PM on September 17, 2012


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