When I took delivery of my Crossfire, the moron lot boy at the dealership put about 3/4 of a tank of regular in it. I noticed quite a bit of hesitation and stumbling, especially in stop-and-go traffic. Adding octane boost didn't really help, but once I'd managed to burn off that tankful, the car ran much better (flawlessly) on 93 octane. So I can attest that regular isn't going to make it in the Crossfire.