What causes metal shavings?
Without proper lubrication, the heat and friction between the metal parts would create small metal shavings. Metal shavings vary in size, but most of them are microscopic. What causes metal shavings in the oil? Along with regular wear and tear, one of the major contributors to a buildup of metal shavings in engine oil includes bearing damage. Engine bearings (including main, connecting rod, small-end and camshaft bearings) are often bi-metal or tri-metal structures.