In looking up your compressor....
I assume you have an oil ' tank' on it which can be checked for oil level ?
as compared to the R4 which does not have one....
Does your new receiver dryer say anything about adding oil to it just prior to installation?
If you decide to add oil ... I would put it in between the condenser and the receiver dryer... not slug the TXValve....
For R12 I suggest Castrol premium cold flow mineral oil part number 6912 from Cleburne , Tx... Which is what Carlisle Auto Air in San Antonio suggested when I was buying AC stuff....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html