Which of the following is NOT a listed cause of high oil consumption?

• A. Failing or failed bearing
• B. Worn piston rings
• C. External oil leakage
• D. Engine breather or vacuum pump breather

Answer: (D)

Understanding what typically causes high oil consumption helps you pinpoint the issue quickly. The main culprits are mechanical wear and external losses that directly reduce the oil remaining in the engine or allow oil to burn.

A failing or failed bearing disrupts the normal oil control within the crankcase, which can lead to oil being consumed more rapidly. Worn piston rings fail to seal the piston-cylinder gap, allowing oil to creep past into the combustion chamber where it’s burned, increasing listed oil usage. External oil leakage is a straight loss path—the oil escapes the engine rather than being burned or used for lubrication—so you’ll see increased consumption in the sense of reduced oil in the system and/or visible leaks.

The engine breather or vacuum pump breather, while important for venting crankcase gases and controlling pressure, is not considered a listed cause of high oil consumption in this context. Problems with the breather affect crankcase pressure and oil mist handling, but they aren’t identified as a primary listed cause of increased oil consumption in the referenced material.