Yes, like a light oil - 5w and some kerosene, diesel etc - just to flush contamination- however, typically the spindle box is not subjected to a lot of crap - run it for a while with the original oil to warm things up, drain into a clean container (I use something with a white bottom) and see what you have draining out. If it is pretty clean and no metallic particles, I will just add some clean oil with the drain open to flush a bit, then fill up with the 30w. Remember that these Utilathes were supplied to schools, military, industry to work - us home dudes will not typically drive the lathe to its limits and also, lubes and such have greatly increased in quality since 1950’s.