In spectrometric oil analysis, copper in the oil indicates wear of which component?

• A. Main bearings or bushings.
• B. Pistons or wrist pin plugs.
• C. Cylinder walls or piston rings.
• D. Camshaft.

Answer: (A)

Copper in the oil points to bearing wear, specifically from the main bearings or bushings. Bearings are made with copper-containing alloys, and as these bearing surfaces wear against the crankshaft journals, small copper particles shed into the oil. Piston rings or cylinder walls usually wear to release iron and aluminum from those components, not copper. Camshafts are typically steel or iron, so their wear shows up as iron-related metals rather than copper. So detecting copper in the oil is a sign that the bearings are the worn parts.