2007 Chrysler Crossfire Owner Manual - Page 186

186 STARTING AND OPERATING FUEL REQUIREMENTS Your engine is designed to meet all emissions regulations and provide satisfactory fuel economy and optimum performance when using high quality unleaded gasoline having an octane rating of 91 or higher. DaimlerChrysler Corporation requires the use of 91 octane or higher premium fuel to minimize the potential for engine damage. Light spark knock at low engine speeds is not harmful to your engine. However, continued heavy spark knock at high speeds can cause damage and should be reported to your authorized dealer immediately. Engine damage resulting from operating with a heavy spark knock may not be covered by the new vehicle warranty. Poor quality gasoline can cause problems such as hard starting, stalling and stumble. If you experience these problems, try another brand of gasoline before considering service for the vehicle.