The original compressor in my 01 4.4i is a Denso. Their name (and the oil quantity) appears on the clutch end that you can probably see with a mirror (or use your camera phone like an inspection camera like I do).

For that compressor (part numbers listed above), the nominal oil fill is 110 CC of ND-8 oil. Denso tech support suggested that oil, but also said PAG-46 can be substituted as ND-8 can be hard to find.

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David.X5
2001 X5 4.4i Sport
SOLD! at 160k miles