What can cause compression loss in an engine?

Compression loss in an engine is primarily caused by issues that prevent the proper sealing of the combustion chamber. An out-of-round cylinder wall can lead to a decreased ability of the piston rings to maintain an effective seal against the cylinder walls.

When a cylinder wall is .010" out of round, it affects how uniformly the piston compresses air in the cylinder. If the cylinder is not perfectly cylindrical, it can create gaps where combustion gases can escape past the piston rings, resulting in lower compression readings. Proper compression is crucial for engine performance, efficiency, and power generation.

In contrast, while oil ring end gaps do play a role in controlling oil consumption and may affect engine lubrication, they do not directly cause compression loss in the way that a physical deformation of the cylinder wall does. An incorrect oil piston ring also won't specifically relate to compression loss unless it fails to properly match with the cylinder specifications.