Theory Of Operation

A 100 ml or larger graduated cylinder is recommended for this test because it makes it easier to determine the percentage of ethanol without having to do the math to figure out the percentage. If this is not available, another measuring device can be used or you could use a ruler in a straight-sided glass cup or jar.

The idea is that when you mix water with gas, any ethanol in the gas combines with and joins the water, separating from the fuel. If you know how much water you initially added to the gas, subtract that out of the clear layer at the bottom of your graduated cylinder at the end of the experiment, and the rest of the clear substance is ethanol.

If you are not using the same volumes of fuel and water called out in the test procedure the formula to determine the percentage of ethanol in the fuel is as follows:

• (Clear fluid - Water added = ethanol) divided by (Gas) multiplied by (100) = ethanol percentage
• Example given for a vehicle that has 20% ethanol, Put 5" of gas plus 1" of water in a glass jar and shake well > (2" clear fluid - 1" of water = 1" ethanol), divided by (5" of gas) multiplied by 100) = 20% ethanol