'Synthetic lubricants' combine a whole host of lubricants, although they differ in their composition and properties. However, they aren't always compatible – or can't always be mixed – with other synthetic lubricants or mineral base oils.
Like their mineral counterparts, synthetic lubricants aren't manufactured based on crude oil, but on natural gas derivatives or other raw materials. Polyalphaolefins (PAO), which rank among the most common synthetic base oils, are made from ethylene and unsaturated hydrocarbons, for example. These hydrocarbons are mainly extracted from natural gas, and their molecules are converted using a chemical process (polymerisation) under the influence of catalysts. The hydrocarbons' low-viscosity, low-molecular-weight compounds (monomers) are linked to lubricating macromolecules (polymers) through chain growth reactions.
Unlike mineral oils, where a single batch of oil can contain millions of different molecular structures, the molecular sizes and shapes present in a synthetic oil are far more homogeneous. In addition, the chemically converted molecules show significantly higher levels of consistency, proving far more resistant and able to better withstand the harsh operating conditions without oxidising or thermally decomposing. This results in one of the largest benefits of synthetic lubricants: they can be used for far longer than mineral lubricants (even at elevated operating temperatures), which contributes to engines and machines being run sustainably. A further benefit of synthetic base oils is their higher viscosity index (VI). This is calculated using the viscosities measured at 40°C and 100°C. The higher the viscosity index of an oil, the lower its viscosity changes with the temperature. Due to their good viscosity temperature behaviour, synthetic lubricants can often be selected for certain applications requiring a lower viscosity than mineral lubricants. This minimises the inevitable splash and friction losses during lubrication, which in turn opens up huge potential for energy savings. The low-viscosity, synthetic-based, premium engine oils we see today are likely the best-known example of how synthetic lubricants can reduce friction and increase energy efficiency at the same time. Whereas in the past, multigrade engine oils previously had a viscosity of mostly SAE 20W-50, today it's often SAE 0W-20 and below. Low viscosity synthetic oils allow engines to run increasingly smoothly and consume less fuel.
This principle also suggests that the operation of hydraulics, bearings and gears can also benefit from synthetic lubricants if, for example, a synthetic hydraulic oil HLP 32 is used instead of a mineral HLP 46, or a synthetic CLP 220 is used instead of a mineral CLP 320 for gear oils. Thin oils also transfer heat better, which offers a few key advantages: The reduction in friction, which is further heightened with new, organometallic additives, means the temperature at the friction point and the amount of oil needed to fill the system falls. Tank volumes may be reduced during the design phase, thanks to the oil being under less thermal stress and oxidation and oil ageing slowing down. The oil also remains usable for longer. The lubricated component surfaces are smoother due to the influence of additives. A stable lubricating film that prevents abrasive wear forms more easily. This leads to components being less susceptible to requiring repair and their downtime being reduced.
Low-viscosity synthetic lubricants can reduce energy losses in such a way that energy-consuming production facilities need less energy in operation or energy-generating facilities produce greater amounts of electricity.
Overall, lubricants based on synthetic base oils enable a greater sustainable use of lubricants as well as the components supplied by them, which all contributes to reducing CO2 emissions.