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. says

    In response to some of the inaccurate comments listed above: Quik-Check ™ Solution, spelled “Quik”, like “Quik-Trip” Gas Station Chain, not “quick”…Is NOT “food-coloring” dye or even similar to “food coloring dyes” – Food coloring solutions bought at your local supermarket are NOT safe for your fuel system (will water contaminate fuel) – Unlike our Quik-Check “dye” Solution (very concentrated indicator which instantly reveals alcohol + water presence in fuel/gasoline/petroleum/oils), which can be squirted back into your fuel tank, after testing- Yes, it will likely turn plastic, (fuel-tester plastic test tubes, rubber tanks and hoses blue (over time) since it is VERY concentrated, but it will NOT contaminate fuel or damage your fuel system.
    #2: Our Quik-Check Solution (RT=registered trademark), which we refer to as “QCS” has been used in the petroleum industry and aircraft industry for many years. Gas service industry uses it for filtering out gas tanks contaminated with water and/or alcohol (typically 20,000-40,000 gas tanks, so obviously they use more than just 1 drop) – When all water and alcohol filtered out (with advanced costly equipment), they confirm gas is alcohol and water-free, when visually no longer bright QCS-color blue. We now (couple of years) include our QCS with our complete test kits primarily for ease of visualization (fuel-tester percent markings shown on Daansen model 391S fuel-tester). BUT, since QCS accurately reveals any amount of alcohol or water in fuel, it is used by many (particularly when testing diesel, aircraft fuels, and gas pumps labeled “pure-gas” ethanol-free or E0, which should always have ZERO water or alcohol, unless contaminated).
    BTW, Sample must be agitated (shaken) to assure QCS given opportunity to mix with water or alcohol (if any present) – Typically a sample (E.G. E5/E10/E15) will turnn bright blue, before you even shake, swirl or agitate specimen, after adding 1-2 drops (pint or less sample), but we ADVISE (see QCS instructions supplied with bottles/kits), mixing/agitating specimen just to be sure.
    We have a couple of direct distributors of our QCS solution (carefully chosen) and we do NOT sell quik-check at any retail stores. It is a specialty product, and very useful for those who understand the process of gas/water/alcohol contamination and absorption. As mentioned in your posts, presence of alcohol can (also) be easily determined with * household items (glass jar + water, etc.), but Daansen’s fuel-tester, which is RE-USEABLE (will last a lifetime) at a price of about $10.00 or less, seems a wise investment, for anybody concerned about the quality of the fuel they purchase.
    *Note: As I often explain to the public, in as simple terms as possible, when you combine alcohol + water, 1+1 does NOT equal 2…When alcohol (which is hydroscopic) absorbs water, the VOLUME EXPANDS- Scientific theory that supports all methods that determine alcohol presence and percent in ethanol + water + oil/gas samples. This is at a molecular level…Said another way: 1 oz. water + 1oz. alcohol= about 2.2 ounces, not 2.0. Also helps explain the incidence of gas tank leakage, when somebody foolishly leaves a full tank of E10 gas for prolonged period of time. Since ethanol can absorb more than 50% of it’s volume, a 5% or less space=tank 95% full, may not be enough when tank in a moist environment. Typically this occurs to boat owners who leave E10 tank 95% full over winter, outside – But I have received several reports over the years of fires caused (all engine types, including small aircraft) due to fuel tank seepage (caused by volume expansion after ethanol water-absorption/phase-separation- Danger and serious hazard/accident, (fuel leaking out of tank and/or fire) caused solely because of water-contaminated ethanol fuel blends. Feel free to contact me directly if you need any additional information – If you prefer to purchase our QCS from an aircraft distributor, visit EAA- They only offer our 6ml size bottle at the present time – Our websites offer 6ml (180 drops/tests), 10ml, 15ml and other sizes. We only supply pint/quart sizes of QCS directly to petroleum service industry companies, not the public. EAA test kit with QCS link:
    Fuel-Testers Company Quik-Check order page:

  2. KW says

    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.

  3. 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.


    • Joe says

      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.


  4. says

    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.

  5. Joe says

    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?

    • Lee says

      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

      • joe says

        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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