I am replacing my R4 style A/C compressor this weekend. The job seems straight forward after reading a bunch of posts with one exception. How and when should I add the oil charge to the compressor so that it doesn't all run out during the installation? The compressor has stickers that state it was shipped dry. Should it be added after it is install through the gauge port on the suction line maybe? Please advise the best method!

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1984 300CD (sold)
1973 220DPK 4 spd (died)
1978 350SL 4 spd gray market
2003 SLK32 AMG
1988 300CE (sold)
1997 E420 (Totaled)
1998 E320 Wagon