some years ago on a 757 Budapest to London:
me sitting by the winder watching the steady flow of oil from the No.2 engine growing larger and steadier by the minute ...
*ding dong*
Me: the flight deck may be aware, but perhaps you might like to let them know they seem to have an oil leak from the No.2 engine....
CC: oh, how do you know that's the No.2 engine - I think that's normal, and the flight deck haven't informed us anything is wrong ....
Me: suit yourself, i'm sure w'll be Ok on one engine - would you like me to let the rest of the passengers know?
CC: that won't be necessary, sir, but thank you anyway...
Me: my pleasure
'Twas dripping nicely after landing, and lots of cowls being flung about after shut down....