Piston
A sliding metal cylinder inside the engine block that compresses the air-fuel mixture and transmits combustion force to the crankshaft.
The piston is one of the most critical moving parts inside an internal combustion engine. It is a cylindrical metal component made of aluminum alloy that fits snugly inside the engine cylinder. The piston's primary job is to compress the air-fuel mixture during the compression stroke and then absorb the massive expansion force of the ignited fuel-air mixture during the power stroke, translating that energy downward into the connecting rod and crankshaft.
To seal the gap between the piston and the cylinder wall, pistons are fitted with springy metal piston rings. These rings prevent combustion gases from blowing past into the oil pan (blow-by) and keep engine oil from entering the combustion chamber.
Pistons operate under extreme temperatures and pressures. Problems like engine overheating, detonation (spark knock), or low oil lubrication can cause severe piston damage, such as cracked skirts, melted crowns, or scuffed cylinder walls. Repairing damaged pistons requires a complete engine rebuild or replacement.