thought it might be slight oil leak.
Just a note regarding semantics - an "oil leak" isn't really what's going on when there's oil on the blades - "oil leak" suggests there's a reservoir of liquid lubricant dribbling out. It's usually solid greases that have dispersed over time, sometimes from cycles of heat and environmental conditions, that eventually get flung around by mechanical action; or lubricants that have off-gassed (heat again?) and resettled, sort of "condensing" on those parts. (I'm no expert though).
They're not an issue until things get sluggish or glued solid, or until some of that crap begins to condense on lens elements. Many people DIY repair them when that happens, or send off to an expert on the gear who can not just clean but adjust. For now I'd run some rolls through it, verify it's giving you proper exposure. If you ever do a shoot where you hire models or if you have a vacation or shooting trip coming where a lens failure could really hurt, I'd consider servicing it if you see any hints of trouble.
DIY lens repair requires a willingness to destroy a lens, or that sort of born-with-it ability to look at a mechanical system and understand what everything does, at a glance. (My brother has that, I most certainly do not).
