My wife never forgets anything (especially when I screw up) and when we went to get some gas today I naturally went for premium since that was what I was used to in my previous car (this was the first time at the pump with the prius). My wife quickly yelled at me and informed me that during the orientation that I got when I bought the prius, I was informed not to put in premium and only use regular. I honestly don't remember hearing that but then again I was also too excited about the new car that a lot of what was being said went through one ear and out the other. I believe that they said I had to use gas with no more than 10% ethanol but I never heard premium being bad. Can anyone shed some light on this. We ended up leaving the gas station without filling up due to the fact we couldn't agree on things. Who is right here? Can I use premium or does it have to be regular?