Mercury 2003--Marauder Owner's Manual page 186

Maintenance and Specifications
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.
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