🔍 Key Concepts

• Function of the piston skirt in guiding the piston within the cylinder • Effect of knurling (small ridges/grooves) on metal surfaces • Difference between sealing done by piston rings vs the role of the skirt

💭 Think About

• Think about which part of the piston actually provides the gas-tight seal in a diesel engine. • Ask yourself: what do the small ridges created by knurling tend to do to any oil or lubricant on that surface? • Consider whether knurling makes the piston tighter in the bore for sealing, or shapes the surface to help something else happen between the skirt and cylinder wall.

✅ Before You Answer

• Verify which component mainly provides the compression seal: the piston rings or the skirt. • Consider how a textured surface (knurled) affects the behavior of oil between two sliding surfaces. • Eliminate any option that confuses the role of the rings with the role of the skirt.