Did you use the Automatic Transmission Fluid as suggested above? If so, how did you use it and what were your impressions of it?
I don't have any experience with it so these questions are at least naive, and perhaps just plain dumb. How would it work in an ultrasonic cleaner? Is it a fire hazard and flammable? Does it evaporate quickly? Is it hazardous indoors?
ATF is basically a light weight oil with several different additives.
I wouldn't use it in a ultrasonic cleaner. Most people use it as a penetrating oil.
Most ultrasonic cleaners say to use water or solvent.