What is a common consequence of using old lubricating oil?

Using old lubricating oil commonly leads to reduced lubrication efficiency. As oil ages, it undergoes chemical changes due to oxidation, contamination, and the breakdown of additives. These processes diminish the oil's ability to form a protective film on moving parts, which is essential for effective lubrication. As a result, the oil may fail to adequately reduce friction and wear in machinery, leading to potential damage or reduced operational efficiency.

While increased viscosity, thinning of the oil, and formation of sludge are also effects that can occur as oil degrades, reduced lubrication efficiency encapsulates the broader impact on the system, highlighting the crucial role of oil quality in maintaining optimal machine performance. Old oil limits its functional capabilities, making lubrication less effective.