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.
Flew a lot in DC-3's, DC-6 and 7's, Connies. My favorites were Electras and Convair 330's. Loved the exhaust glowing blue on the Convairs.
Remember the United Constellation(I think,may have been a DC-7) that ditched between Hawaii and California, circa 1959? I think all were saved by the Coast Guard.
I flew in a DC-4 from Winnipeg to Churchill, Manitoba, and observed a similar oil flow. Apparently this was normal operation.