Ford 2002 Excursion Owner's Manual page 22

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
0W-30
F˚ -20 -10 0 10 20 30 40
C˚ -30 -25
EXPECTED TEMPERATURE RANGE
22
* 15W-40 Preferred
Preferred 10W-30
5W-30
50 60 70 80 90 100
-20 -15 -10 -5 0 5 10 15 20 25 30 35 40