have a friend with an ethanol test kit. he went around a couple of years ago testing the amount of ethanol in various brands of gas. he found out most of your cheaper "off brands" had much less than the name brands, some almost zero. the sticker on the pumps says "may contain up to 10%" the ethanol is added when the gas is delivered to the station. the tanker gets 90% gas and then blends up to 10% ethanol and depends on the sloshing and movement to the station to blend.
here is a link for a test kit, but i just made one out of a caper bottle
http://www.amazon.com/Briggs-Stratto...ethanol+tester