What is the function of the lower piston rings?

• A. Oil control or scraper type designed to prevent lubricating oil from entering and being burnt in the combustion space.
• B. They seal the combustion chamber against gas leakage.
• C. They transfer heat from the piston to the cylinder wall.
• D. They provide a path for cooling air to the piston crown.

Answer: (A)

The lower piston rings are the oil control (scraper) rings. Their job is to wipe excess lubricating oil off the cylinder wall and return it to the crankcase, preventing oil from entering the combustion chamber where it would burn. This keeps oil consumption down and reduces smoke and carbon buildup, while still maintaining a thin lubricating film on the wall. They don’t seal the combustion chamber (that’s the job of the compression rings) and they don’t provide a path for cooling air to the piston crown. While some heat is transferred through the rings, their main function is oil management, not heat transfer.