What are typical causes and consequences of oil-system contamination?

• A. Dirt and water cause improved lubrication.
• B. Metal wear particles cause increased performance.
• C. Water intrusion does not affect oil filters.
• D. Dirt, metal wear particles, and water intrusion causing reduced lubrication, filter plugging, and bearing damage.

Answer: (D)

Oil-system contamination comes from dirt, water, and metal wear particles entering the oil. Dirt and water can get in through seals, intake or condensate, and condensation effects, while metal wear particles come from internal engine wear. These contaminants disrupt lubrication by preventing the oil from forming a stable film, increasing friction and wear. Dirt and particles can clog filters and oil passages, reducing flow and stressing bearings. Water in oil weakens lubrication, promotes corrosion, and can form emulsions that dull film strength. Metal wear particles act as hard abrasives that accelerate bearing and gear damage. Because all three contaminants can be present and lead to reduced lubrication, filter plugging, and bearing damage, this option best captures typical causes and consequences.