Here in the part of California we are in, e-10 ethanol in pump gasoline is mandatory. They tried something else in the 90's (MTBE) but it was getting into the ground water and lakes. I keep accurate logs of mpg for all our cars and know exactly how they perform. The two FI ones are quite stable however every once in awhile the mileage would drop significantly . Several times it dropped the same week on both cars that use the same station. Since then we changed stations. The way the laws read here, the percentage of alcohol is regulated, but not the percentage of water in that alcohol. So what we think happens is once in a while someone has cut the fuel with water intentionally or unintentionally. Since ethanol will absorb water, it would be easy to add some water to the tanker, or tanks and dilute the fuel. From research, E10 will hold up to 3 teaspoons of water per gallon. That is 11.7 gallons per full tanker truck. 3 loads a day X 11.7 gallons X $3 gallon wholesale then = $105 a day extra in one's pocket, and no one would see it. For station tanks multiply that by the number of tanks. The ethanol in the fuel would absorb it, and then it would go thru the system with slightly reduced power. I suspect this is what happens. This may not happen in other parts of the US or Canada but I am 99% sure it does here. There is no way two of our cars would both drop 3 to 4 mpg the same week, same station pumps, same driving conditions. I am tired of rebuilding small equipment carbs that fail with this ethanol fuel, and I do blame it for the increase in problems.