2008 Jeep Wrangler Owner's Manual - Page 385

384 MAINTAINING YOUR VEHICLE CAUTION! Overfilling or underfilling the crankcase will cause aeration or loss of oil pressure. This could damage your engine. Change Engine Oil Refer to the Maintenance Schedule in Section 8 for recommended engine oil change intervals. Engine Oil Selection For best performance and maximum protection for all engines under all types of operating conditions, the manufacturer recommends engine oils that are API Certified and meet the requirements of DaimlerChrysler Material Standard MS-6395. American Petroleum Institute (API) Engine Oil Identification Symbol This symbol means that the oil has been certified by the American Petroleum Institute (API). The manufacturer only recommends API Certified engine oils. Engine Oil Viscosity (3.8L Engines) SAE 5W-20 engine oil is recommended for all operating temperatures. This engine oil improves low temperature starting and vehicle fuel economy. The engine oil filler cap also shows the recommended engine oil viscosity for your engine. For information on engine oil filler cap location, refer to the "Engine Compartment" illustration in this section.