While the word synthetic often can be a negative term, implying something artificial or cheap, in lubrication, just the opposite is true. Synthetic lubricants, overall, have superior performance characteristics compared to their petroleum counterparts (see Table I). While they may be more expensive, in this case, “synthetic” means improved.
Defining synthetic lubricants In general, the synthetic designation applies to products whose basestocks have been manufactured as opposed to being extracted from naturally occurring petroleum. Synthetic lubricants are different from conventional petroleumbased oils because their molecular structures are custom designed and tailored to meet specific performance criteria.
Most petroleum-based and synthetic lubricants consist of a basestock and various additives selected to improve or supplement the lubricant’s performance. The basestock is the primary component—usually 70% to 90%—of the finished lubricant. Its structure and stability determines the flow characteristics of the oil, as well as its temperature range, volatility, lubricity and cleanliness. Since the basestock is the dominant component, one way to make a better lubricant is to start with a better basestock.
The following list highlights the various types of basestocks used to formulate synthetic lubricants along with their principal applications.
- Polyalphaolefins and dialkylated benzenes provide performance similar to mineral oils and are compatible with them. They are used as hydraulic fluids and gear, bearing lubricants and compressor lubricants.
- Dibasic acid and polyol esters readily accept additives, which make them excellent compressor lubricants.
- Polyglycols are used primarily for lubricating gears and bearings.
- Phosphate esters provide fire resistance. Silicones are nontoxic, fire resistant and water repellant.
Additives enhance basestock properties or add new ones, such as improved stability at high and low temperatures, modified flow properties and reduced wear, friction and corrosion. Basestocks and additives must be selected carefully and balanced to allow the finished lubricant to do its job—which includes protecting moving parts from wear, removing heat and dirt, preventing rust and corrosion, improving energy efficiency and extending lubricant life. Synthetic lubricants can provide economic advantages when used in place of petroleum-based lubricants. These benefits include:
- Improved energy efficiency
- Wider operating temperature range
- Increased performance ratings
- Reduced maintenance
- Better reliability and safer performance
For best results, users should consult with the manufacturer prior to selecting synthetic lubricants. While they have outstanding performance characteristics, the proper choices must be made to ensure that the right product is chosen for any given application.
Joe Foszcz is a contributing editor to Lubrication Management & Technology. For more information, e-mail him directly: firstname.lastname@example.org