The question has been answered like 10 times!!! Run what ever you want!!! I personally run premium in mine for the reason I explained in my previous post. That's what is recommended, but apparently not required, per FCA. I don't mind paying a couple bucks more per tank full for the piece of mind. Top tier fuel only as well, because not all fuel is created equal, also explained in several previous posts...(- ;Wow, this thread suddenly went south fast. What does a Ford Crown Vic have to do with the OP’s question? And octane is a measurement not a thing, it cant “compress”; does nothing to answer the OP’s question....