Purchased a small kit ($7.99) at my local Sea Plane base in Tavares Florida. Just a glass tube with various lines molded in the tube. Add water to the water line. Add gasoline to the gasoline line. Shake and let sit for 5 to 10 minutes, then read the line where the water now sits. These lines read 5%, 10%, 15% up to 30%. Tried it twice so far. Once at an Exxon Premium pump and once at a discount premium pump. Both times, it read that the gas had 5% alcohol. Will take more readings whenever I get fuel, both regular and premium, just to see. Something that was interesting is that with the test, I remember something that my teachers said wayyyyyyy back when I was in High School. If you mix an equal amount of water and alcohol, you will not get twice the amount of liquid. Example. If you mix one pint of water with one pint of alcohol, you will NOT get two pints of liquid, but you will get somewhat less than two pints. See, I remember my High School teachers. The reason being that alcohol molecules are smaller than water molocules, and they fit between the larger water molocules. The reason I mention this is that when I took the reading, showing the fuel had 5% alcohol, the total amount of liquid in the glass tube went down. Matter of fact, it went down more than the amount the water/alcohol mix went up.