Particles, especially catalytic metal particles like copper, iron and increase the rate at which oxidation occurs. Particles also strip the oil of its polar additives, rust inhibitors and dispersants. Also, numerous very small particles in stable suspension can cause the oil’s vissosity to increase.
Abrasive particles are responsible for much of the wear leading to premsture failure of mechanical components. Under sliding condition, clearance – sized particles enter the oil film between surfaces and cut away material much like a lathe cuts metal. Under rolling contact condition, particles transfer concentrated load between two surfaces in relative motion, resulting in surface fatigue, pitting, and spalling. Particles contaminated oil travelling at high velocity can also cause erosive wear.