Well-oiled Machines

 You know the phrase "it runs like a well-oiled machine?" The machine is built of precisely defined gears, to within a specified tolerance, and it is designed to do exactly the same thing every time without fail. But what about the oil? Oil is black, sticky stuff, derived from heating, compression, and distillation over millions of years from the decayed remains of life in the jungle. Even if it is clear when you add it in, it soon becomes black, sticky stuff that gets on everything and between everything and is impossible to get off when it touches you.

A well-oiled machine needs both: the gears, and the oil.