Soluble oil in radiators? You bet! I believe it was more common in the South than up here in the North country, but we used to run it in heavy equipment engines that were freshly rebuilt. The oil kept things from rusting internally and provided lubrication for the coolant pump during the first fifty or hundred hours or so after overhaul. At that point the break-in oil and the coolant would be changed out for standard fluids. The coolant system needed a good flush before switching to ethylene glycol antifreeze, but it worked very well.
As for running it in a mister, I suppose one could use it, but I stick with Kool Mist and Rustlick Syncool. I have no problems milling 303 with either one.