Question 76Motor Plants - 1st Asst/Chief

The correct answer is B) An extremely high neutralization number. The neutralization number of a diesel engine's lube oil is considered the most significant factor in determining whether the oil should be drained and renewed. An extremely high neutralization number indicates that the oil has become excessively acidic, which can lead to corrosion and damage to the engine components. This is the primary regulatory requirement for determining when lube oil should be changed in diesel-powered vessels. The other options are not as reliable indicators. A black color may simply indicate normal engine use, and an extremely low precipitation number or an increase in flash point are not direct measures of the oil's acidity and ability to protect the engine.