What happens to the viscosity of an oil as it oxidizes?

As oil oxidizes, the chemical structure of the oil changes due to reactions with oxygen, resulting in the formation of various byproducts, such as sludge, varnish, and acids. These changes increase the molecular weight and complexity of the oil, leading to an increase in viscosity.

Higher viscosity means the oil becomes thicker and more resistant to flow, which can negatively impact the lubrication properties and the performance of machinery. Increased viscosity can cause problems such as reduced pumpability, increased friction, overheating, and ultimately decreased efficiency of the machinery being lubricated.

Therefore, as oil undergoes oxidation, its viscosity tends to increase, which is crucial for understanding how oil degradation can affect equipment performance and longevity.