FORD 2005 F-550 v.2 - Manual (Page 254)

Engine oil and filter recommendations
Look for this certification
trademark.
Use SAE 5W-20 engine oil.
Only use oils “Certified For Gasoline Engines” by the American
Petroleum Institute (API). An oil with this trademark symbol conforms
to the current engine and emission system protection standards and fuel
economy requirements of the International Lubricant Standardization and
Approval Committee (ISLAC), comprised of U.S. and Japanese
automobile manufacturers.
To protect your engine’s warranty use Motorcraft SAE 5W-20 or an
equivalent 5W-20 oil meeting Ford specification WSS-M2C930-A. SAE
5W-20 oil provides optimum fuel economy and durability
performance meeting all requirements for your vehicle’s engine.
Do not use supplemental engine oil additives, cleaners or other engine
treatments. They are unnecessary and could lead to engine damage that
is not covered by Ford warranty.
Change your engine oil and filter according to the appropriate schedule
listed in the scheduled maintenance guide.
Ford production and aftermarket (Motorcraft) oil filters are designed for
added engine protection and long life. If a replacement oil filter is used
that does not meet Ford material and design specifications, start-up
engine noises or knock may be experienced.
It is recommended you use the appropriate Motorcraft oil filter (or
another brand meeting Ford specifications) for your engine application.
2005 F250/350/450/550 (f23)
Owners Guide (post-2002-fmt)
USA_English (fus)
Maintenance and Specifications
254