Group IV base oils are polyalphaolefins (PAO) that consist exclusively of a carbon and hydrogen, usually in a straight chain with periodic branching. PAO’s do not contain any sulphur, nitrogen, wax, or ringed structures, as opposed to a refined mineral oil. This level of purity is achieved because a PAO is designed and made (synthesized) rather than being refined from crude oil as is done with mineral oils. The consistency of a PAO imparts excellent cold temperature properties, a high viscosity index (VI), and excellent resistance to oxidation. However, one drawback to PAOs is that they will not dissolve additives as well as a mineral oil.
Group V base oils are described as all other synthesized hydrocarbons that are not PAO’s, such as: polyalkylene glycol (PAG), phosphate ester, and other ester base oils. Group V base oils contain more than just carbon and hydrogen, such as oxygen and phosphorus, in the base oil backbone. These other atoms impart unique properties to the base oil when compared to a PAO. For example, ester base oils have excellent solubility and are often added in a small percentage to a PAO to increase additive solvency. Ester base oils are inherently resistant to temperature breakdown and have excellent detergency. Phosphate esters are used as fire-resistant hydraulic oils and PAG’s have a very high VI, usually water soluble, with great high and low temperature properties.
Each synthetic base oil has its pros and cons and selecting and testing the best base oil (or combination of base oils) during lubricant formulation based on the intended application is key.
I hope this post was a helpful reminder of the need for Group IV and V synthetic base oils in different types of lubricants. If you have any questions about the different lubricants used in your operation or potential opportunities for consolidation – don’t hesitate to reach out via the comments section below.
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Excellent reminder. Thanks for posting Marcel.