What is a common cause of excessive lube oil consumption in engines?

Worn or broken piston rings are a common cause of excessive lube oil consumption in engines because they play a critical role in maintaining the seal between the combustion chamber and the crankcase. When piston rings are worn down or damaged, they can no longer effectively contain the combustion gases and prevent oil from entering the combustion chamber. This can lead to increased oil burning during the combustion process, resulting in higher oil consumption.

Additionally, the wear or damage to piston rings can also allow oil vapor to escape into the combustion chamber, further contributing to oil loss. Other engine components, such as valve seals, can also affect oil consumption, but the condition of the piston rings is particularly significant since they directly interact with the moving pistons and the combustion process. Understanding this will help in diagnosing and addressing issues with oil consumption in an engine.