Kushmin_05h

I've noticed recently with my B6 S4 that my mileage is noticably worse running non ethanol premium fuel, I believe the E and non E premium around here are both 91 octane. But with the Non Ethanol fuel I lose 2-5mpg making the same trip at the same speeds on average, and have had people tell me with the Non Ethanol that my car sounds like it's running rough. I thought the opposite would be true, but I too noticed it sounded a lil bit rough on the non ethanol, almost like it's misfiring, thats what actually prompted me into lookin into my mileage difference between the two. Has anyone else had these results? I ran the tank of Non ethanol out of it and filled back up with 91 at the pumps, the 10% you find most everywhere and the engine smoothed back out and mileage is back to where I see it usually. So either Stewart's Non Ethanol is total junk, or has water in their tanks, or the Ethanol fuel is just better for this car.

ehj

Mileage for my 2012 A5 is not as important to me as ensuring a long life for the engine. Here in southern Utah 10% ethanol-free is only 88 octane. Audi says use 93 but as a minimum 91. Without considering mileage which is better in the long run?