2004 Chrysler PT Cruiser Owner's Manual - Page 216

216 STARTING AND OPERATING FUEL REQUIREMENTS 2.4L Standard Engine and 2.4L Standard Turbo Engine Your vehicle is designed to meet all emission regulations and provide excellent fuel economy when using high quality regular unleaded gasoline with an octane rating of 87. The use of premium gasoline is not recommended. The use of premium gasoline will provide no benefit over high quality regular gasolines, and in some circumstances, may result in poorer performance. 2.4L High Output Turbo Engine Your engine is designed to meet all emission regulations and provide excellent fuel economy and performance when using high quality unleaded gasoline having an octane rating of 91. The purchase of higher octane is not required. The use of high quality unleaded gasoline having an octane rating of 91 is recommended but not required. High quality unleaded gasoline having a minumum octane rating of 87 may safely be used for your vehicle. Use of these lower octane gasolines, however, may result in reduced acceleration performance. 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 immediate service is required. 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 hesitations. If you experience these symptoms, try another brand of gasoline (with the appropriate octane rating for your engine) before considering service for the vehicle.