Question 378General Subjects - 1st Asst/Chief

The correct answer is C) Wear of various lead-bronze alloy bearings. Elevated copper levels in used diesel engine crankcase lubricating oil indicate wear of lead-bronze alloy bearings. Lead-bronze alloy bearings are commonly used in diesel engine crankshafts and connecting rods. As these bearings wear, they release copper particles into the lubricating oil, leading to elevated copper concentrations detected during oil analysis. The other options are incorrect because: A) Aluminum-alloy bearings would not be a source of elevated copper. B) Piston ring wear would not typically result in elevated copper. D) White metal alloy bearings, which are tin-based, would not be a source of copper contamination.