FORD 2003 Mustang v.1 - Manual (Page 202)

Engine oil and filter recommendations
Look for this
certification trademark.
SAE 5W-20 engine oil is recommended.
Only use oils “Certified For Gasoline Engines” by the
American Petroleum Institute (API). Use Motorcraft
or an equivalent oil meeting Ford specification
WSS-M2C153–H. 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, oil
treatments or engine treatments. They are
unnecessary and could, under certain conditions,
lead to engine damage which is not covered by your
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.
Maintenance and Specifications
202