testing gas for ethanol questions?

i have been mixing different ratios of reg and 100 LL gas in my RV for years. finally decided to test some samples. i took a extra fuel sampler and marker the half way point with a black line. it measured 2 3/4 inches to the black line. i filled it to the black line with H2O, then topped off with regular sunoco gas. shook it up then let it settle for a minute. it raised up 5/16 inch. questions? does this sound like a propper way to do this? what formula would you used to figure % ethanol in the fuel?

Ed,

That is the way to do it.

The tester you can buy from the EAA is marked so you can tell how much ethanol is in the mogas. What you are doing will simply tell you there is some in there, not how much.

BTW, the tester only requires about an inch of water.

does it give you.........

a % reading of ethanol. anyone have a pic of the unit?

The water/alcohol layer should be relatively clear after setting for a little while. When you have a cloudy layer, commonly referred to as the 'rag layer', you cannot accurately calculate the amount of that layer. It is amazing how much it will reduce with a little bit of time.

AS&S has a nice pre-marked unit for $5.99. I got one and it is really nice. I use a rubber stopper from the hardware store to shake it up.
http://www.aircraftspruce.com/catalog/appages/gasoholTester.php

EAA's procedure for testing autogas is as follows:

Graduated Cylinder Method - To 9 parts of gasoline (900 ml), add 100 ml of water for a total of 1000 ml in the graduated cylinder. Shake thoroughly, let stand for 10 minutes or until gasoline is again bright and clear. Record the apparent level of the line between the gasoline and water. This ?Final Volume? is used in the calculation below.

You will note 9 parts of gasoline to 1 part water, not 50/50.

This is what I have done for years. If there is ethanol, it clearly shows.