If it's not leaking, you're out of oil
That about sums it up.
An oldie but a goody: Q: What is the difference between a DC-6 and a DC-7
Answer: A DC-6 is four engine aeroplane with three blade props, a DC-7 is a three engine aeroplane with four blade props.
Buried in the reams of wonderful stuff in the Qantas Foundation museum is a monograph that chronicles the travels of one Wright 3340 out of a QF L-1049G, from the time it left the overhaul shop at Sydney, until it got back about two years later, where it had been repaired, which aeroplanes/airline it had found itself fitted to, until the next failure.
Quite an amazing saga, on one occasion every every Connie in the QF fleet was on the ground, somehwere, with an engine failure. The Liberator and Lanc. that were used to ferry engines around used to be kept very busy.
One hairy technique: Engine cowls iced up badly around the intake, resulting in rising CHT. If the cowl gills were opened, to increase airflow, the drag would cause a problem maintaining IAS/Altitude, not a good idea over big hill.
The answer was to feather each engine in turn, the training edge of the prop. blade would machine off enough ice to restore cooling airflow. We don't know we are alive, these days. To the best of my knowledge, Pakistani was the ONLY airline to finish the Connie era with the same number of aeroplanes it started with, not even QF managed that.
Tootle pip!!