Lubrication Consulting / 5 min
Synthetic or Mineral Oil? Base Oil Selection in Industrial Lubricants
70% to 95% of an industrial lubricant's content is base oil. The quality of the base oil directly determines the product's heat resistance, service life and viscosity index (VI). As application conditions become more demanding, mineral base oils give way to advanced synthetic base oils.
Published by: Rotek Technical Content Team
Content is published based on manufacturer technical documentation and equipment requirements as the basis for final selection. This is general guidance and does not replace equipment-specific manufacturer approval.
Review our editorial guidelinesTable of Contents
- - The Limits of Mineral Base Oils
- - PAO (Polyalphaolefin) Synthetic Oils
- - PAG (Polyalkylene Glycol) Technology
- - Synthetic Ester Oils and Their Uses
The Limits of Mineral Base Oils
Mineral oils, refined from crude petroleum, cover the large majority of general industrial applications (standard hydraulics, medium-load reducers). However, when operating temperature exceeds 80°C they oxidize quickly, and at very low temperatures they wax and lose fluidity.
PAO (Polyalphaolefin) Synthetic Oils
PAO (Group IV) oils, synthesized in a lab, are molecularly fully uniform. They have a much higher Viscosity Index (stability against temperature change) than mineral oils, and are generally used in enclosed gears and compressors operating across a wide range from extreme cold to extreme heat.
PAG (Polyalkylene Glycol) Technology
PAG (Group V) synthetic oils are among the base oils with the lowest coefficient of friction. In worm-gear reducers with very high sliding friction, they dramatically lower temperature. However, they never mix with mineral or PAO oils, and can be incompatible with polyurethane-based seals.
Synthetic Ester Oils and Their Uses
Ester (Group V) based synthetic oils have excellent adhesion (polarity) to metals. They evaporate cleanly without residue at very high temperatures (for example 250°C oven chain oils) and, being readily biodegradable in nature, are often preferred in environmentally sensitive applications.
Frequently Asked Questions
Can synthetic oil be mixed with mineral oil?
PAO (Polyalphaolefin) synthetic oils and most esters can be mixed with mineral oils. However, PAG (Polyalkylene Glycol) based synthetic oils must NEVER be mixed with mineral or PAO oils — mixing causes serious chemical precipitation in the system.
Why is PAG synthetic oil used in worm-gear reducers?
In worm gears, the gears slide over one another (rather than rolling), generating extreme heat. Because PAG-based synthetic oil has very high slipperiness, it dramatically reduces friction and energy loss compared with mineral oil.
Does switching to synthetic oil lower maintenance cost?
Yes. Although synthetic oil costs more per liter than mineral oil, it offers 3-4 times the service life. By protecting equipment, it significantly reduces downtime, filter changes and waste-oil costs.
What does viscosity index (VI) mean?
Viscosity index (VI) expresses an oil's resistance to fluidity change with temperature. The higher the VI (as with synthetic oils), the less the oil thickens in the cold and the less it thins in the heat — meaning excellent film protection.