I've read in several places online that ethanol can be removed from gasoline by adding water, mixing vigorously, and allowing the water and gas to separate. From what I've read, it seems that ethanol dissolves better in water than in gas, so the separated water will carry most of the ethanol with it and can be removed to leave ethanol-free gas. Does this method really work, and are there any adverse effects on the resulting gas?

  • 1
    Yes, you have described a correct procedure for separating the ethanol out of an ethanol/gasoline mix. But you DO NOT want to use this as motor fuel as it will be LOW octane gasoline and you may damage your engine due to pre-ignition. If you really want or need ethanol-free (i.e. E0) gasoline, there are places that sell it. Many Farm Bureau Coop locations sell it and many marinas sell it. It's usually somewhat more expensive but I used it in my lawn and garden tools to avoid carb issues.
    – jwh20
    Commented Dec 9, 2019 at 23:34
  • @jwh20 Right, buying it from a gas station would be ideal, but I don't know of any gas stations around me that sell it. The nearest one I can find online is 45 minutes of driving in the opposite direction of anywhere else I normally go, so it'd be an hour and a half of driving just to get some gas. It's possible that there are others that haven't been mapped, and I'll keep looking, but I thought it was interesting that this was even possible and wanted to see if it was a realistic method or if, like you said, it would result in lower-quality gas.
    – zaen
    Commented Dec 10, 2019 at 3:46

3 Answers 3


I would suggest you could get this to work, however, it may be a lot more trouble than what it's worth. Please note: I'm not a chemist (nor did I sleep at a Holiday Inn Express last night). Please read what I've written with that in mind.

According to this website what you are suggesting would work. Ethanol absorbs water, which also means, ethanol is attracted to water. That said, if by introduction of water into the fuel, then agitating the mixture to disburse the water throughout the fuel, the ethanol should be attracted to the water in the process. Because water is heavier than the fuel, it will settle out over time. With it goes the ethanol. Then by a process of pouring off the fuel, you should have pure fuel without ethanol in it.

There are some caveats.

  • Gasoline (fuel/octane/petrol) is flammable. Treat it appropriately and respectfully.
  • You need to ensure you mix the right amount of water into the fuel. This is the sticking point. What is the right amount? I'm not sure ... are you? Using too much might foul your mixture. Using too little won't get rid of all the ethanol. I'm sure this could be figure out through mathematics, however the key would be the percentage of ethanol being used in the fuel. While the pump at the fueling station may say it contains 10% ethanol, that's more of a guideline than a cold hard fact. You'd need some way to measure the ethanol content directly. There are tools out there to do it, then you'd have to precisely measure how much water to add in the process to get it right.

As long as things are done correctly, the resultant fuel should be fairly clear of either water or ethanol. Would it be a process I'd undertake? Absolutely not. Fuel should stay in the fuel tank or gas can. Keep it there and leave it well enough alone. JMHO, though. Do as you please and at your own risk. I don't condone it and I'm sure SE wouldn't condone it either (though I do not speak for the company or site).

Another link I used.


Ethanol is soluble in gasoline and water. Ethanol and water mix is soluble to some degree in gasoline. In the good old days before ethanol in gasoline , one added a little alcohol (eg. Heet) to gasoline so that the gasoline could absorb a trace of water and not have a water phase that would separate and freeze in the gas lines ( in winter). So it is possible to add water to 10% ethanol gasoline and get a separate alcohol/water phase. A chemist would need to say how much water would need to added to get most of the alcohol out of the gasoline, my educated guess would be about 10% water. You now have a significant amount of water/ethanol to dispose of. And the remaining gasoline is saturated with water , although that is not very much water, it can and will separate and cause frozen fuel lines in cold weather. So feasible, but I would say dumb. I expect is is difficult to get a number for the solubility of water in gasoline ; Refinery chemists tell me this is a difficult job. Evidence that the water is in the gasoline is the fact that corrosion inhibitors must be added to product pipelines because after miles of travel in the cool buried pipeline water collects on the steel surface and can cause corrosion . Also . the pipelines need to be "pigged" ( cleaned ) of water pools in the low spots.


This process does work, and I use it to provide ethanol free (or really low ethanol content) gasoline for my outdoor equipment. The ratio of 1 cup water to 1 gallon gasoline is usually recommended and what I use. Add the water to the gas can on the way to the station, fill, and between filling and the ride home, it's mixed. Allow to sit at least several hours to separate. Overnight or longer is better. You can either transfer to another gas can, remembering to not take the last gallon or so, or refill your equipment carefully, so as not to agitate and mix the separated water/ethanol/gas. The Water/ethanol mix that remains is essentially denatured alcohol, with extra water, and maybe used as such, or disposed of.

Last thought - Ethanol does increase the Octane rating of the gas, but only by a few counts. So start with a mid grade or higher octane if you're going to use it in an engine that needs the anti-knock properties. If I recall correctly, its a drop of between 2-3 on the rating, not so much that the average engine would notice, but makeing 80 octane from 84 might not work in some engines. Your mileage may vary...

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