2005 Jeep Liberty Owner's Manual - Page 315

MAINTAINING YOUR VEHICLE 315 Engine Oil Selection (Diesel Engines) For best performance and maximum protection for all engines under all types of operating conditions, the manufacturer recommends using synthetic engine oils that are API Certified (SL/CF), and meet the requirements of DaimlerChrysler Material Standard MS-10725. Engine Oil Viscosity (2.8L Diesel Engines) Use SAE 0W-40 Mobil 1 Synthetic Engine Oil that meets API categories CF or better and the requirements of DaimlerChrysler Material Standard MS-10725. If you cannot find SAE 0W-40, then SAE 5W-40 Mobil 1 Synthetic Engine Oil is acceptable. Any engine oil that does not meet the manufacturer's requirements should not be used. Lubricants which do not have both, the engine oil certification mark and the correct SAE viscosity grade number should not be used. Synthetic Engine Oils - All Engines There are a number of engine oils being promoted as either synthetic or semi-synthetic. If you chose to use such a product, use only those oils that are certified by the American Petroleum Institute (API) to display the symbol on the front of the container or the proper ACEA category and show the recommended SAE viscosity grade. Follow the service schedule that describes your driving type. Materials Added To Engine Oils The manufacturer strongly recommends against the addition of any additives (other than leak detection dyes) to engine oil. Engine oil is an engineered product and it's performance may be impaired by supplemental additives. 7