Taken from
http://www.ehow.com/list_6322727_sew...ernatives.html
"Marvel Mystery Oil was developed in 1923 to fight carburetor corrosion and buildup. Company founders keep the oil formula a secret to this today, but it is effective in fixing a variety of engine problems. Although the oil type is a mystery, this oil is light enough to maintain small, motorized appliances--including a sewing machine."
I also noticed that the Marvel Mystery Oil site states that the oil was formulated for carburetor corrosion, nothing to do with sewing machines.