Ethanol testing made easy

GAfuels readers already know of the many advantages to using mogas in aircraft approved for its use. Not only does its save them $1.40-$1.50 per gallon compared to avgas, but these pilots are making real progress in reducing lead emissions from general aviation, the only significant consumer of leaded fuel on the planet.

While your bloggers would always recommend obtaining aviation-grade mogas directly from a fuel terminal, and have it delivered and stored in aviation-grade fuel equipment at your airport, in many instances the gasoline obtainable at retail gas stations and marinas is quite suitable for aircraft, provided it has the correct octane (AKI) rating and contains no ethanol. It is absolutely necessary to check each and every batch of fuel obtained from retail sellers of gasoline for the presence of ethanol, regardless how the pump may be labeled. (Fuel contamination is rare, but occurs for every type of fuel, including avgas and Jet-A).

Fortunately, it is easy, quick and cheap to check for ethanol’s presence in fuel. Petersen Aviation describes how this is done with a simple olive jar and a small amount of water. It even offers a reusable tester for a small fee. offers its Quick Check Solution that makes use of a special dye.

Recently a member of the Aviation Fuel Club, Gilbert Pierce of Germantown, Tenn., sent us the description of how he tests for ethanol using a few drops of ordinary food coloring:

“While driving 20 miles into Mississippi to get ethanol-free gasoline for my airplane I was contemplating what must be in the blue dye that is in the Quick Check Solution kit. It occurred to me that what ever it was had to be water soluble so it would mix with the ethanol.  I always check the suppliers of ethanol-free fuel before pumping any gas as I have been lied to about it. Anyway, the test kit that you add water to is a hassle and takes a few minutes to settle out. The blue Fuel-Check works great but is expensive. When I got home I got my wife’s red, blue and green food coloring out; it’s water soluble. A quick check with pint jars of ethanol-free fuel and adulterated fuel indicated that a drop of any color food coloring will dissolve and turn the adulterated fuel the same color as the food coloring.  Putting a drop of food coloring in pure gasoline, the drop just goes to the bottom of the sample and rolls around there as little globules. Now I just carry a bottle of inexpensive and readily obtainable food coloring and a quart glass jar – it’s easier to get a fuel sample into – and have an instant indication of ethanol free fuel or adulterated fuel.”

Remember, always test every batch of gasoline purchased at any location other than an airport — “Let the buyer beware” !

The GAfuels Blog is written by two private pilots concerned about the future availability of fuels for piston-engine aircraft: Dean Billing, Sisters, Ore., a pilot, homebuilder and expert on autogas and ethanol, and Kent Misegades, Cary, N.C., an aerospace engineer, aviation sales rep for U-Fuel, and president of EAA1114.


  1. It’s been months since the last question, with no answers.

    I would sure like a simple, fast way to tell if the gas is all gas.

  2. Mark Priglmeier says:

    My results using the (Schilling) food coloring were inconclusive using ten percent ethanol and pure mogas. Both fuels had globs. When mixed vigorously, then settled, I found ambiguous results.

    But now the water test using the ethanol fuel tester was completely accurate. Tested right to the ten percent line with the ethanol gas. I will stick with my tester. It works. Inexpensive. Accurate.

    My examination for what is worth.


    • I bought the quickcheck blue dye solution and it dissolved (turned the fuel blue) in the fuel I tested with water in a graduated cylinder. First I put in 10 ml.of water and then added 50 ml.of ethanol fuel. Shake vigorously. The water level went up to 13 ml. and the total was just a bit less than 60 ml. I am not a chemist but I understand that if you mix water and alcohol you get less volume total than each individually. I have also heard that all the ethanol will not combine with the water. Maybe 30% stays in the fuel sample. Anyway I mixed my ethanol fuel with some that does not have any ethanol 50 / 50. The quickcheck fluid did NOT dissolve. It did like the food coloring I tried. Just made a glob at the bottom. I called the co. and talked to the owner. She said it would detect less than 1% ethanol. My results say not. I would appreciate any info on my methods.


  3. None of the planes I currently fly are certified for MoGas but the fuel systems in the boats I run don’t like ethanol either.

    If this test really works, I’ll share it with the Sport Pilots who stop by KPWT.

  4. We tried McCormick Food color and egg dye and also Betty Crocker Gel Food Colors in a known sample of mid-grade gasoline with 10% ethanol. Neither food coloring dissolved. Both stayed as a blob on the bottom. What brand or type of food coloring are you using?

    • I’d like to see a response to Joe, his point is reasonable and if there is a type/brand that actually works there is an aircraft forum with 1210 members, including myself, that is eager to know this, otherwise this article could be misleading one to believe their fuel to be alcohol free when it is an ethanol blend after all. This wouldn’t be nearly as important if it was concerning fuel for a leaf blower. Thanks

    • Was the mid-grade fuel labelled “MAY contain up to 10% ethanol”. It could have none in it, thus your results.

      • Fuel was tested with a graduated cylinder.

        A small amount of water in first then fill with fuel, shake well, level of water goes up calculate percent of alcohol.

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