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Easy test for Ethanol in Fuel


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Hey Raiders,

I posted this in another topic, but think it's worth its own space.

There is a fairly easy method to test if the fuel you purchased or the fuel in your tank has ethanol:

1. Get a small clear petrol resistant container with a lid eg small clear bottle. Something narrow like one of those condiment bottles is easiest to work with.

2. Put a small amount of pure water in the container and mark the top of the liquid with a line on the outside of the container.

3. Fill the container near to the top with the fuel.   Close the container and shake then leave it to sit until the fuel and water separate into different layers.

4. If the water level is higher than the mark you made previously on the side of the container than the fuel contains ethanol. 

This works because of what ethanol is:


The Ethanol molecule has two sides.

One side is organic (carbons and hydrogen atoms and this side allows it to mix into oils and fuels, because thats what oils and distillates are - varying length Carbon and Hydrogen chains).

The other side of the molecule is basically an Oxygen and Hydrogen atom. This Hydroxyl OH side likes to mix with Water as water (H2O) is basically Hydrogen and Oxygen. This side is more polar than the organic side and hence the ethanol molecule prefers to mix into water, rather then in the fuel. The little bit of water you first added in the container draws out the ethanol from the fuel mixture...and you would see that as increased volume of water in your test.

Unless you are as diligent as @Fab1, rarely do people empty or use all of their boat tank fuel. Often the fuel in the tank sits around for some time. In the tank, any water condensation draws out the ethanol and it starts to form a water/ethanol mixture which over time breaks down into basically vinegar (acetic acid). This is the corrosive part that can eat into copper/brass/ally carburettor and other components unless they were designed to cope with that.   

Cheers Zoran

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