Oilers/Plant Tenders (HHC) Civil Service Practice Exam

How does water generally enter a diesel lubricating oil system?

1. Leakage from hoses

2. Condensation of combustion products

3. Direct exposure to rain

4. Faulty seals

The correct answer is: Condensation of combustion products

Water typically enters a diesel lubricating oil system primarily through the condensation of combustion products. During the operation of a diesel engine, the combustion of fuel produces water vapor as a byproduct. As the engine cools down, this vapor condenses into liquid water, which can then mix with the lubricating oil. This is especially prevalent in environments with fluctuating temperatures, where condensation is more likely to occur when the engine temperature decreases after shutdown. While other methods, such as leakage from hoses or faulty seals, can introduce water into the system, these occurrences are generally less common compared to the condensation process. Direct exposure to rain is also a potential source, but it is less significant in the context of a closed lubricating system designed to minimize exposure to external weather conditions. Hence, the condensation of combustion products represents the primary mechanism by which water infiltrates the diesel lubricating oil system.