2004 Jeep Grand Cherokee Owner's Manual - Page 221

STARTING AND OPERATING 221 NOTE: The Tire Pressure Monitor system must be retrained following a tire rotation. See your authorized dealer for service. The suggested rotation method is the "forward-cross" shown in the following diagram. FUEL REQUIREMENTS Your engine is designed to meet all emissions regulations and provide excellent fuel economy and performance when using high quality unleaded gasoline having 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 gasoline, and in some circumstances may result in poorer performance. NOTE: 4.7L HO Engines (If Equipped): High quality premium unleaded gasoline with an octane rating of 91 is recommended but not required. 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 operation with a heavy spark knock may not be covered by the new vehicle warranty. 5