I was traveling in IOWA and had to put fill up my 2003 Audi A6 3.0 with fuel that had ethanol. There was no fuel without this additive. Ever since then my fuel economy has decreased from about 19 to 17, even after filling up with premium unleaded again.

Is ethanol bad for my car?
Is this the reason for the deacrease in fuel ecomony?
What do I need to do increase my fuel economy?

 

What was the percentage of ethanol in the fuel? 10% - E10? 85% - E85?

10% not bad for you car. Ethanol does have a lower energy value and you will get lower mileage as a result. Did you go through the full tank before filling or have you been adding to the Ethanol that was already there? E10 will not damage your car.

85%, which I doubt since you are still driving the car, would have not been so good.

Anyway, I'm guessing you ran E10 through your car so don't sweat it. If you mileage doesn't come back I would assume something else is wrong.

 

There are lots of stations using E10 gas now. Ethenol is a high octane fuel but as stated, it needs 25% more fuel to reach the same a/f. You have nothing to worry about performance or durability wise since its not enough to really affect anything but a mpg or 2 change. Just calm down and you will be ok