Where does the greatest amount of wear occur on the cylinder walls of a normally operating engine?

The greatest amount of wear on the cylinder walls of a normally operating engine occurs near the top of the cylinder. This increased wear is primarily due to the high temperatures and pressures that exist in this region during the combustion cycle.

As the piston moves to the top of the cylinder during the compression stroke, it encounters the combustion gases, which are at peak pressure when ignition happens. The fluctuations between the high-temperature combustion gases and the mechanical forces exerted on the piston create conditions that contribute to increased wear near the top. Additionally, the oil film that lubricates the cylinder walls tends to be thinnest at the top, leading to a reduction in lubrication and increased friction with the piston rings.

In contrast, wear is less pronounced near the bottom of the cylinder where the piston moves slower and where the oil film is thicker, providing better lubrication and reduced friction. This understanding of wear patterns is crucial for maintaining engine longevity and ensuring efficient operation.