With thanks to some old-timers, I dispensed with "model railroad" product oil - good ol' Penn 5w-20 is great for anywhere in a loco, wheelset, etc. that slides - oil is good. But after a couple of years of doing that over a larger collection of locos, some of them began squeaking and squawing (lol) at me. I called Jeff at the Train Tender who is a fount of toy train knowledge and he got me to go with red grease and a bit of 5w-30 mixed into a 'paste' to lube engine bearings, shafts, etc. Squeaks are gone after break-in time...