Mercury 1999 Villager Owner's Manual page 196

Maintenance and care
Engine oil and filter recommendations
Look for this Certification
Trademark.
Use SAE 5W-30 motor oil certified for gasoline engines by the American
Petroleum Institute (API).
Motor oil displaying the API Certification Trademark will meet all
requirements for your vehicle's engine.
Ford oil specification is WSS-M2C153-G.
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.
It is recommended that you replace the engine oil drain plug washer
each time the engine oil is changed.
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, startup
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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