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Ethanol removal


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As often happens when sat in a classic in a car park people approach for a chat about the car or classics generally.

Recently that happened to me. The person said he had a collection of cars and bikes. We got round to the subject of petrol, specifically ethanol in petrol. He went on to explain how he removes the ethanol from the petrol he uses, having used the method for years.

The method he described was to put water in the petrol, shake the container up, leave the liquid to settle, then siphon the petrol off because the water has dropped to the bottom with the ethanol in it!?

I can understand the logic given that ethanol is apparently hygroscopic, hence the problem with steel petrol tanks rusting, ethanol has scavenged water from the air and the water/ethanol has dropped to the bottom of the tank.

He said that the petrol can then be stored for months/years and he uses the method before he lays his cars up for winter and longer.

Anyone tried this or can comment on the science?   


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The internet is full of 'advice' about how to do this.   If you are comfortable with handling large quantities of highly inflammable liquid at home, then good luck to you.   In particular in disposing of the gallons of contaminated water that should not be poured down the drain!

If you just want to protect your car during storage, then buy one of the many fuel stabilisers available, add it to your tank and take your Triumph for a drive to flush it through the system.   See: https://www.clubtriumph.co.uk/forums/topic/17730-fuel-stabilizer/#comment-192898

Also make sure that all the fuel hoses are of ethanol-resistant material.

Good luck!


Edited by JohnD
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The science is correct in it will remove the vast majority of the ethanol.

Where it falls down is what the petrol you are left with is like. It will have been carefully formulated to meet 95 or whatever octane with the ethanol. What is the new octane? What else has been removed? probably drops a few octane points (ethanol increases the octane rating of petrol, so removing it will reduce it)

Next, what are the practicalities of it? You can't do it on a petrol station forecourt. So you have to buy fuel a couple of gallons at a time, spend time/effort to produce your homebrew petrol with lower octane, and then put it in your car. To get a full tank I need 8 gallons. On some trips I do 4-600 miles in a day. So totally impractical.


A better solution is to chuck some additive in if you don't use the car much. Better still, change the hoses to proper R9, and use the car more

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3 hours ago, Nick Jones said:

Maybe ok for garden machinery or vintage motorbike. The volumes would be more or less practical and those engines probably won’t care much about octane loss.


That was my main reason for asking, chainsaws etc.

As for my cars, yes to all of the above, additive, hoses etc. etc. but I go for the least ethanol possible E5 for example.

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A few months ago I read an article by a chemist who works for the petroleum companies. The lady explained that washing petrol will not only take out the ethanol but it will also remove all the other additives, such as detergents and stabiliser’s.

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Yes, I fear that people who want to do this are the same as those who objected to these damned new machine looms!

IE Luddites.

And the same as those who told Nebuchadnezzar that his 'wheel' thing was evil, and Ug that this 'fire' thing was a gross safety risk in the family cave.

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