Introduction

Ester base stocks provide the ultimate protection for high performance lubricants. The folks at www.teknorapex.com sum it up nicely: “Synthetic esters, with their polarity and uniform structure, provide multiple high performance functions in lubricants.  As a base stock or as an additive, esters improve lubricity, improve the solubility of additives, have an affinity for metal surface, and improve cleanliness and sludge control. They provide or enhance seal and gasket compatibility.  Versus mineral oils, the ester structure offers lower volatility at lower molecular weight and lower viscosity. Esters can be selected to provide extreme high temperature performance, extreme low temp performance, or both. They generally offer high thermal-oxidative stability and biodegradability.”

Advantages

The advantages of ester base stocks include:

• Better Clinging Ability & Protection – Ester base stocks are polar which gives them a better ability to adhere to metal surfaces thus reducing friction and wear under the most adverse conditions.
• Low Evaporation Loss – Esters have low evaporation rates as measured by NOACK Volatility tests (ASTM D5800) which provides a better ability to maintain their viscosity without thinning or evaporating during high temperature operation.

• More Thermally Stable – Esters have a better ability to perform in extreme heat thus resisting breakdown and the formation of varnish or sludge under high heat conditions.
• Better Cold Flow – Esters provide better protection during start up because they remain fluid during low temperature conditions.
• Cleanliness – Esters have a natural ability to clean by dissolving varnish, sludge, and carbon deposits while keeping them in suspension.
• Highly Soluble – Esters have a better ability to blend with other base stocks and additives.
• Environmentally Friendly – Esters are mainly biodegradable and non-toxic.

Many synthetic engine oils are formulated with some ester to increase performance; however, the percentages are often low since ester base stocks are very expensive. The esters most often included in these formulations include: 

Di-Esters – Provide better ability to flow in cold temperatures and are very soluble which aids in blending with other base stock and additives.          

Polyolesters (POE) —  Provide thermal and oxidative stability with low volatility enabling them to outperform other base stock in extreme heat. These are the base stocks of choice for jet engines and heavy duty gas turbines.

Conclusion

For the ultimate in protection, power, and performance, ester base stocks provide a superior building block for lubricants for any engine. Although the use of ester base stocks is often limited due to high costs, when properly blended with other high quality base stocks and additives, ester base stocks will protect engine components under the most adverse conditions.