2007 Jeep Liberty Owner's Manual - Page 273

STARTING AND OPERATING 273 FUEL REQUIREMENTS (GASOLINE ENGINES) 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. Mid-grade gasoline (89 octane) will enhance engine performance during the following conditions: • Hot weather • Towing • Hard accelerations • Hilly terrain • Low humidity 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. Poor quality gasoline can cause problems such as hard starting, stalling and hesitations. If you experience these symptoms, try another brand of "regular" gasoline before considering service for the vehicle. Over 40 auto manufacturer's world wide have issued and endorsed consistent gasoline specifications (the Worldwide Fuel Charter, WWFC) to define fuel properties necessary to deliver enhanced emissions, performance, and durability for your vehicle. The manufacturer recommends the use of gasoline that meets the WWFC specifications if they are available. 5