Oil Consumption - Damaged Piston Rings

The purpose of the piston rings is to separate the combustion chamber from the crankcase by providing a seal. If this seal is not sufficient, engine oil enters the combustion chamber and is burned.

Piston Rings
Piston Rings

The main purpose of piston rings is to provide a seal between the combustion chamber and the crankcase. If this sealing is not sufficient, the oil is no longer scraped off the cylinder wall down into the sump. Instead it accumulates until it enters the combustion chamber and is burned.

If this is combined with fuel flooding, the oil is further diluted increasing oil consumption (as more oil enters the combustion chamber) and the wear increases on the engine components.

Damaged piston rings (due to dirt, lack of lubrication, heat, etc.) will provide insufficient sealing. Incorrectly installed piston rings after a recent overhaul will also result in insufficient sealing. This can be due to broken piston rings, jammed piston rings, incorrectly installed piston rings or overstretched piston rings (during installation).

Compression testing can be used to identify lack of compression (lack of sealing capability). If the compression is outside manufacturer’s specified range, and a wet test (compression testing with a small amount of oil added) increases the compression, then it can be indicator of damaged piston rings (but it also may be other components such as valves).