Lubricating oil, sometimes simply called lubricant/lube, is a class of oils used to reduce the friction, heat, and wear between mechanical components that are in contact with each other. Lubricating oil is used in motorized vehicles, where it is known specifically as motor oil and transmission fluid.
There are two basic categories of lubricating oil: mineral and synthetic. Mineral oils are lubricating oils refined from naturally occurring crude oil. Synthetic oils are lubricating oils that are manufactured. Mineral lubricating oils are currently the most commonly used type because of the low cost of extracting the oils from crude oil. Additionally, mineral oils can be manufactured to have a varying viscosity, therefore making them useful in a wide range of applications.
Lubricating oils of different viscosities can be blended together, and it is this ability to blend them that makes some oils so useful. For example, common motor oil - shown in Figure 1 - is generally a blend of low viscosity oil to allow for easy starting at cool temperatures and a high viscosity oil for better performance at normal running temperatures.
The use of lubricating oils in vehicles is vital to their operation. When an engine is properly lubricated, it needs to put less work into moving pistons as the pistons glide easily. In the long run, this means that the car is able to operate while using less fuel and run at a lower temperature. Overall, the proper use of lubricating oil in a car improves efficiency and reduces the amount of wear and tear on moving engine parts.
Since lubricating oils are such a valuable resource, there have been many efforts to recycle used oils. Used lubricating oil is recycled at "re-refineries", where water is removed from the oil in a process of dehydration. Impurities within the used oil - such as industrial fuel - are separated out and the oil is captured using vacuum distillation. This leaves behind a heavy waste that contains oil additives and byproducts. The extracted lubricating oil then undergoes a series of refining processes to remove other impurities. Once refined, the oil is separated into three different viscosities for a variety of uses.
For a more in-depth look at the oil recycling process, click here.