I think I'm going to kill a gas station employee. Maybe.. This morning I took my son to school and had to stop to get gas. I have always used premium fuel in the little devil, no matter how much the few extra bucks were. This morning when I ran into pay I pointed to their little indicator, paid and went to pump. The cashier was talking to a friend and not paying attention. When I was pumping I didn't notice the difference until it was done. (It's 7 degrees and I was making faces at my son and trying to stay warm.) There was almost 3/4 tank when I was done and should have only been 1/2. I noticed this right away and wasn't sure what to do. She drove fine the rest of the trip to school and home. She was even ok on a quick trip to the store, but when I started her up to come home all hell broke loose. Her EPC and ASR*/ESP* lights came on and stayed on. She idled really rough and had little to no power. It felt like she wanted to stall in neutral. I came home right away and jumped on here. I don't hear a knocking but the whole car seems to shake a little. And the breaks were not as responsive. Could this be due to a lower octane gas or higher ethanol content? And if so, how do I fix her???