3 eng' cruise.
In order to do a three engine ferry on a Comet (RR Avons) the oil system had to be filled to overflowing to allow for oil loss. The engine would still be rotating but would have no air pressure to seal the labryinth seals and the oil would run out.
This would be the same on many other engines although some, (VC-10) had a way of fitting a kit or a long piece of wood to prevent rotation and prevent loss of oil.
Remember that these are straight jets, or minimal by-pass (Conway) which do not have the drag of a big fan so fuel was not so much of an issue.
How the Speys in the Nimrod do it, for endurance, I have no clue but they must have a different or bigger oil system.
Hope this helps.