I always refuel at the same Chevron gas station in Virginia on the way to work. Since last month the pumps have E10 labels on them. My 2003 Toyota Echo (47k miles on the engine) is equipped with a knock sensor, and the owner's manual states that the engine will run with E10. My experience is the engine does feel more responsive and stronger as I step on the gas padel. However, the engine idle is a bit unstable which goes back and forth between 7k and 8k RPM as the engine vibrates (not sure if this is called knocking). I always clean TB/IAC/MAF plus a bottle of Techron in the gas tank every 1500 miles. I wonder if this rough idle has to do with E10 or my automatic transmission is going bad. Does anyone using E10 have the similar experience with the engine performance? So far, I donot see any drop in gas mileage. I am getting 45-47 MPG on E10 with the same gas pump. Should I switch to another Chevron gas station in Maryland that sells straight gas?