1999 Ford F350 7.3L Diesel Supplement 1st Printing - Page 23

General maintenance information Engine oil specifications To help achieve proper engine performance and durability, it is important that only engine lubricating oils of the proper quality are used in your diesel engine and that the engine oil is changed no later than the recommended interval. Diesel engines require specially formulated oil to resist contamination. Proper quality oils also provide maximum efficiency of the crankcase ventilating system which reduces air pollution. For normal or severe service, use Motorcraft oil or an equivalent oil conforming to Ford Specification WSS-M2C171-C or API Service categories CG-4/SH. Do not use oil labeled with only one of the following category designations; SG, SH, CE, CF-4, or CG-4, as they could cause engine damage. Engine oils with improved fuel economy properties (energy conserving) are currently available. If you use an energy conserving oil, be sure it meets the recommended Ford Specification, API service categories and SAE viscosity grades listed in the Lubricant and Maintenance Materials Specifications chart. Some energy conserving oils do not meet the requirements necessary for your diesel engine. SAE VISCOSITY GRADES * Preferred 5W-30 0W-30 F˚ C˚ 15W-40 Preferred 10W-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 EXPECTED TEMPERATURE RANGE The use of correct oil viscosities for diesel engines is important for satisfactory operation. Determine which oil viscosity best suits the temperature range you expect to encounter for the next service interval. 23