In the 1960s when I worked in a service bay I was told to use the copper washer on the engine drain plug if fitted and for the rest of the engine, gearbox and back axle just nip up the drain/filler plugs. No fancy sealants, never had any leaks. Back street boys?
Correct - Sump plug usually has a straight thread so needs a washer, gearbox and axles usually have a taper thread so 'should' seal themselves, but over time the threads wear.
