What is the primary function of a piston ring in a combustion engine?

The primary function of a piston ring in a combustion engine is to seal the combustion chamber and control oil consumption. Piston rings are essential because they create a tight seal between the piston and the cylinder wall, preventing the escape of combustion gases during the power stroke. This sealing action maximizes the engine's efficiency by ensuring that the pressure generated during combustion is utilized effectively to produce power.

Additionally, piston rings help in controlling oil consumption by scraping excess oil off the cylinder wall and returning it to the oil sump. This means they play a critical role in maintaining the proper oil film on cylinder walls, which helps lubricate the moving parts and reduce wear while also preventing the engine from consuming excessive oil, which can lead to increased emissions and contamination of the combustion chamber.

The other options, while relevant to engine operation, do not accurately describe the primary purpose of piston rings. Increasing air intake efficiency, cooling engine components, and improving fuel atomization are functions served by different components or systems within the engine.