Question 201Motor Plants - Assistant Engineer

The correct answer is A) An extremely high neutralization number. The neutralization number is a key indicator of the condition of the diesel-generator's lube oil. A high neutralization number suggests that the oil has become acidic and needs to be replaced, as the acidity can lead to corrosion and damage to the engine components. This is the most significant factor in determining whether the lube oil should be drained and renewed, as it directly reflects the oil's quality and ability to continue providing proper lubrication. The other options are not as significant in this determination. A low precipitation number, oil appearing black in color, or an increase in flash point may indicate other issues, but do not necessarily mean the oil needs to be changed as urgently as a high neutralization number.