This allowed moving parts of a machine to be oiled while it ran

Answer: Lubrication

Moving parts of early machines were able to run because of the application of a lubricant such as oil, vaseline or grease.

The history of lubrication has advanced into a discipline known as tribology, which studies interactions between the moving parts of a machine.

By studying friction, wear, and lubrication, engineers are able to design bearings that prolong the useful life of rotating machinery.