Hi folks,  I also have a few experiences with different oils and
electric motors.  As I also do work on old cars and other machines, I
have learned that most oils contain acids which corrode and eat metals,
especially if they are not changed regularly.  Ever wondered why
plastic gets eaten by oil?  (It cracks and gets hard, etc.)

Well, to lubricate a bushing or bearing with oil, so that no damage
occurs to the metal parts if the oil is never changed, one must at all
cost use acid-free oil.  These oils are available, and a very good
source is liquid paraffin from the nearest chemist.  Also, some sewing
machine oils are acid-free for this very purpose -- one has to ask a
supplier.

One last source of good acid-free oil is so called "grandfather clock"
oil as supplied by watchmakers' supply companies.  Sometimes this is a
bit thin but different ones are available.

All normal oils as used for motor cars and other purposes are not
suitable: they all contain acid.  One could try to use automotive
automatic transmission oil.  This should be acid-free and is red in
colour (please verify).  Synthetic oils are not necessarily usable
either: I once lost a plastic oil-level-inspection window in a machine
because the new "wonderful" synthetic oil (very expensive) dissolved it
within 2 days.

Regards,

Bernt Damm

 [ I'm afraid that automatic transmission fluid compromises lubricating
 [ properties for high-temperature stability.  That's why it's called a
 [ fluid, not oil.  "3-in-1" oil, and similar penetrating oils with
 [ included acids, are especially good for cutting the rust in, for
 [ example, children's toys left out-of-doors!  For electric motors,
 [ follow the advice of the motor specialists and use a real acid-free
 [ lubricating oil designed for that service.  It will already contain
 [ any additives that have been proven beneficial.  -- Robbie