What might cause an engine to have low compression?

Low compression in an engine is often caused by worn or broken piston rings. Piston rings are crucial for maintaining the seal between the piston and the cylinder wall. Their primary function is to ensure that combustion gases do not escape the combustion chamber and that oil does not leak into the combustion space. When the rings are worn or damaged, it leads to a loss of compression because the gases can escape past the rings, reducing the effectiveness of the engine’s compressive force during the power stroke.

The combustion process relies on maintaining high pressure within the cylinders to create the necessary power. Low compression can result in poor engine performance, decreased power output, difficulties starting the engine, and increased emissions. Thus, assessing the condition of piston rings is a critical aspect of diagnosing low compression issues in an engine.

Other options presented, such as excessive engine oil, improper fuel mixture, and overcooling of the engine, do not directly cause low compression in the way that worn or broken piston rings do. Excessive oil can lead to fouling of spark plugs or oil burning but does not affect the compression seal. An improper fuel mixture may cause issues in fuel combustion but won't inherently lower the cylinder compression. Overcooling could lead to performance problems but does not affect the mechanical