plus a few older types suffer from oil weeping past seals and causing air quality issues.
Do not have to be older types, even some of the newer types, like the APS3200 still have regular failures with total oil loss through the compressor and out the turbine and exhaust. Smoke plume over several bays (Bleed OFF) or in the cabin (Bleed ON), the oil tank emptied in a few minutes, low oil pressure, then silence.
