🔍 Key Concepts

• piston ring function in sealing combustion gases and controlling lubrication • effects of lubrication and friction on metal-to-metal contact • consequences of improper material hardness or ring movement (scuffing, wear, blow-by)

💭 Think About

• Think about what scuffing actually is at the metal surface between the ring and liner. What operating condition would most directly prevent that metal-to-metal damage? • Which option describes a condition that is always necessary for any piston ring design, regardless of material or engine type? • Consider whether piston rings are designed to compress and rotate somewhat in normal operation, or if they must be rigid and fixed in place.

✅ Before You Answer

• Be clear on how piston rings normally move in the groove during operation (compression and slight rotation). • Consider which factor most directly controls friction and heat at the ring-liner interface. • Eliminate any option that would contradict normal piston ring design and function in internal combustion engines.