Hydraulic fluids are as common as sand on the beach. Each hydraulic fluid has its own special recipe, but we can still find similarities and group the oils. Let's take a closer look at mineral-based and synthetic oils from the three main groups: mineral oil, synthetic oils, and plant oils.
Mineral oils are extracted from crude oil, which determines their basic chemistry. Since every crude oil deposit is made up of different fossils, it affects factors like sulphur content.
Mineral oils are based on hydrocarbons. After extracting the crude oil, it goes to the refinery where it undergoes some processing. The oils can be processed to different extents, but the molecular structure remains largely unchanged. The base oils from different refineries may vary but are generally similar and can be mixed together.
Synthetic oils are also often based on hydrocarbons and can come from crude oil, coal, gas, or plant oils. However, unlike mineral oils, the raw material does not determine the basic chemistry of synthetic oils. In the production of synthetic oils, the raw material is broken down into its individual components and reassembled like building blocks. This makes synthetic oils very diverse; some can be mixed with each other while others cannot.
In conclusion, mineral and synthetic oils can be divided into different groups such as:
(according to standards DIN 51524 / ISO 6743-4)
- Group I
Raffinate second raffinates (HL, HLP, HLPD….): vacuum distillate of crude oil mineral oil raffinate, high quality, VI 80-120 - Group II + III
Hydrocracking oil(HL, HLP, HLPD….): "heat-treated" mineral oil with optimised molecular culture, VI ≥80-120 Group II ; VI ≥120 Group III - Group IV
Poly - a- olefin (PAO): Synthetic base oil with paraffinic base structure, VI ≥135 - Group V
Ester (HFD-R, HFD-U, HFA-E): synthetic and natural liquids obtained from alcohol and acid
Glycols (HFA, HFC): Synthetic polyhydric alcohol obtained from petroleum or coal
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