A lubricant is any substance, usually a liquid, which is used to reduce the friction of two surfaces, improving grip and increasing abrasion resistance. For this purpose, lubricants are injected between two moving surfaces. Lubricants may as well perform additional functions, such as removing foreign particles from surfaces, or dissolving them, as well as removing heat generated by friction.
According to purpose, lubricants are divided into:
  • Hydraulic (forward movement)
  • Motor (car engines et cetera)
    • Two-stroke
    • Four-stroke
  • Turbine (industrial engines, turbines and pumps)
  • Electrical insulating (transformers)
The best-known lubricant is engine oil, which lubricates moving vehicles and other internal combustion engines’ surfaces with similar power.
Typically, motor oil contains about 90% of base oil and about 10% of additives.
Base oils are:
  • Mineral (purified lilac oil fraction)
  • Mineral-synthetic (mineral oil is treated in special ways, usually with hydrogen)
  • Synthetic (manufactured by chemical synthesis with plants: polyolefin, silicon, ester, fluorocarbon oil, et cetera)
Lubricant additives reduce friction and wear, increase viscosity, resistance to corrosion/oxidation, aging et cetera.
Motor lubricants are popularly divided into 3 types:
  • Mineral (based on over 95% mineral oil)
  • Semi-synthetic (over 15% of synthetic additives and synthetic/mineral hydrogenated oils)
  • Synthetic (no or very small amounts of mineral oil)
There is no strict separation. Commercial oil characterization is mainly based on oil properties matching various specifications and marks. Generally, to achieve higher brands or newer specifications, more synthetic additives or better base oil should be added to the composition of the lubricants.