How does an efficient lubricant work when it lubricates mechanical chains?

For it to be effective, a lubricant has to penetrate into the articulation and work in the places where there is friction. It therefore has to be applied:

• on the inside-facing sides of the chain strands. Otherwise, the centrifugal force would prevent it reaching the surfaces that rub together;
• on the slack strands, near where the drive pinion disengages so as to take advantage of the loosening of the articulations in order to reform the oil film which had been partly driven away by the forces exerted on the taut strand, as well as by centrifugal force (there can be additional lubrication points where the drive and driven opinions engage);
• on the interior plates, such that the lubricant works its way between the interior and exterior plates to feed the axle / socket articulations, as well as between the interior plates and the rollers to feed the socket / roller surfaces.

The significant role played by centrifugal force is therefore understood, together with the overall kinetic energy of movement in lubricating articulations: the term used is "lost lubrication". When a chain is correctly lubricated, a film of oil remains in the articulations (mixed lubrication) when movement starts, thus reducing contact between metal surfaces.