Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I believe putting oil directly into the boilerwater, only makes some real sense when it is a tinboiler, as an attempt to form a thin oil film in there, to make them last a bit longer before rusting out. 
Only have two Weedens here, both with brass boilers, and their instruction does not have the oil in the boiler recommendation.
Here they´re oiled by gently tilting the cylinder, to apply some oil inbetween that and the steamchest, a couple of drops on the pistonrod when fully extended, and a few drops sucked in via the exhaust.