I just purchased a Singer walking foot industrial machine 16-188, (there is also a 2 stamped below the model number plate). Before I moved it to my shop, I emptied the open oil well (the oil looked like blackish motor oil) so it wouldn't spill. There was a wick hanging into the oil that apparently lubricated the flywheel, which has 2 leather belts - one to the motor and one up to the sewing head. Both old leather belts are slipping, I assume because they seem to be saturated with oil.
What kind of oil should I use to fill the well? Thank you for any help.