Question 79Motor Plants - 1st Asst/Chief

The correct answer is C) Leaking stuffing boxes introducing cylinder lubricating oil into the crankcase. The reasoning is that when cylinder lubricating oil leaks into the crankcase through faulty stuffing boxes, it can cause the Total Base Number (TBN) of the crankcase lubricating oil to increase. This is because cylinder lubricating oil typically has a higher TBN than crankcase lubricating oil, and the mixing of the two oils results in an overall increase in the TBN of the crankcase lubricating oil. The other options are incorrect because: A) Excessive purification temperatures would more likely lead to a decrease in TBN. B) An increase in water content would not directly lead to an increase in TBN. D) Bearing wear would not directly affect the TBN of the crankcase lubricating oil.