When Should You Use a Synthetic Lubricant? 

Synthetic lubricants encompass a range of compositions that include hydrocarbon bases, polyglycols, organic esters, phosphates, and other materials. Their common feature is that the molecules forming the base lubricant are chemically synthesised to achieve specific properties and a controlled molecular composition. 

For example, fire resistance requirements in aviation hydraulic systems favour the use of phosphate ester-based fluids. The lack of solubility of hydrocarbons and gases in polyalkylene glycol fluids prevents lubricant dilution in natural gas applications. For the purposes of this brief overview, the focus will be on fluids based on synthetic hydrocarbons. 

The decision to use synthetic fluids—which are typically more expensive—will depend on whether the performance requirements justify the additional cost. Systems operating under severe service conditions, extreme temperatures, or extended oil change intervals (either by design or necessity) are the most common criteria for justifying the use of synthetic hydrocarbon-based products. 

Synthetic Lubricant 

Synthetic lubricants are stable at both high and low temperatures. Operating environments that experience extreme temperatures are especially well-suited for these types of products, as they offer better flow at low temperatures as well as increased oxidation stability under high-temperature conditions. 

Products formulated for arctic conditions are typically based on synthetic components. Gearboxes or bearings exposed to excessive heat—whether due to the type of service or environmental conditions—benefit from synthetic lubricants, resulting in extended equipment life and reduced maintenance intervals. 

The combination of high temperatures and oxygen exposure represents an environment where synthetic lubricants perform optimally. They degrade less rapidly in equipment exposed to heat and air, such as compressors and turbochargers. 

In addition to improved performance under extreme temperature conditions, certain installations and systems cannot easily accommodate maintenance or scheduled shutdowns. Lubricants are expected to remain in service for periods that would be detrimental to conventional mineral oil-based fluids. 

Under specific conditions, synthetic lubricants can also help reduce energy consumption, decrease maintenance needs and downtime, and enhance energy production efficiency. 

However, synthetic lubricants do not necessarily provide a cost-benefit advantage or outperform modern mineral oil-based lubricants in environments with constant exposure to contaminants or where operating conditions do not significantly challenge the lubricant’s service life. 

Before opting to use a synthetic lubricant, it is essential to evaluate whether the performance improvements justify the higher cost. Factors to consider include: 

Temperature Extremes 

• Extremely low temperatures. 

• Extremely high temperatures. 

• Thermal cycling between hot and cold. 

Extended Change Intervals Due To: 

• Limited access or convenience. 

• Costs associated with downtime. 

• Maintenance scheduling 

Improved energy efficiency derived from enhanced lubricating film strength and lubricity. 

Excessive oxygen/air exposure combined with high temperatures. 

As noted earlier, synthetic lubricants may not offer added cost benefits over modern conventional lubricants in systems that do not operate under extreme or specialised conditions, or where there is continuous exposure to contaminants. 

Written by: David Doyle, CLS, OMA I, OMA II – ALS Oil&Lubricants