i've been replacing r4's for thirty years and only now
'am i being made aware of this oil passage issue.
r4's are not a bad compressor. originals lasted
years and years. some over ten years.
its the shoddy repair and use of rebuilts that
messes things up. plus not adding oil when servicing them.
if one comes apart then you got something i refer to as
black death. almost everything needs
to be replaced. the evaporator can stay as its single
row and can be flushed. condenser is double row and needs
to be replaced. after everything is done you MUST
install a filter on the suction line just before the comp inlet.
or do the job again.
the r4 comp was designed to be lubed by the oil in
the freon so i'm just not sure that the x is a real issue.
won't hurt though. i'm gonna see if i have a genuine
mb one around and check.

george