What is an piston cooling oil nozzle?

It is a little nozzle which is pointed towards the beneath of a piston in an internal combustion engine.

It is linked to the pressurised side of the oil system, so cool oil coming directly from the oilcooler will spray onto the piston and cooling it instead of just cooling around the cylinder.

This enables the engine to run a much more efficient combustion without the chance of melting a piston or overheating the engine which could lead to engine failure.