Flew to Brazil on a DC-4, 7hrs from Miami to Carracas(sp), another 7hr. from Carracas to Belem. One engine was leaking oil. Oil was running out of the top of the nacelle, down to the trailing edge and into the airstream. I remember pointing it out to the steward. He sloughed it off. I flew in a DC-4 from Winnipeg to Churchill, Manitoba, and observed a similar oil flow. Apparently this was normal operation.
I don't recall flying on a DC-4, 6 or 7 that didn't have oil streaks behind the nacelles. And the streaks invariably got longer and shinier after every take off.
Those old P&W radials were "bad to spit", so to speak.