From "Management of Electronics Assembly" (Ian Oakes)
After talking about 63/37 tin lead alloy and the eutectic point...
"Occasionally, impurities may be added to solder, to vary charactersitics 
within the soldering process in an attempt to improve performance.  For
example, addition of small quantities of antimony and copper can reduce
the amount solder moves under stress when solid.  For particular
applications additions of impurities may be warranted but, in general, it
is best to keep the solder used in a soldering process as pure as possible."

I guess this is the good oil for commercial operations, but it doesn't
mention anything esoteric.