FORD 2003 Ranger v.1 - Manual (Page 197)

Engine Oil Recommendations
2.3L & 3.0L Engines
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SAE 5W-20 engine oil is recommended.
Change your engine oil and filter according to the appropriate schedule
listed in the scheduled maintenance guide.
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.
4.0L Engine
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SAE 5W-30 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-M2C205–A.
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 according to the appropriate schedule listed in
the scheduled maintenance guide.
Maintenance and Specifications
197