132. With a machinery lubricating oil analysis program, it is important to monitor trends over time. What would be indicated by elevated copper levels associated with a recent sample of used diesel engine crankcase lubricating oil?

Elevated copper levels in used diesel engine crankcase lubricating oil indicate wear of lead-bronze alloy bearings, as these bearings are primarily copper-based and release copper particles when worn. Other bearing materials, piston rings, and aluminum-alloy bearings are not primary sources of copper in oil analysis.