Went and did a little reserach instead of just blabberin my mouth off (same thing I get on others about!)...
Polyol esters can extend the high temperature operating range of a lubricant by as much as 50 - 100C due to their superior stability and low volatility. They are also renowned for their film strength and increased lubricity which is useful in reducing energy consumption in many applications. The only downside of polyol esters compared to diesters is their higher price; they are generally 20 - 70% higher on a wholesale basis.
Polyol esters are also the ester of choice for blending with PAOs in passenger car motor oils. This change from lower cost diesters to polyols was driven primarily by the need for reduced fuel consumption and lower volatility in modern specifications. They are used in 2-cycle oils as well for the same reasons plus biodegradability.
In general, polyol esters represent the highest performance level available for high temperature applications at a reasonable price. Although they cost more than many other types of synthetics, the benefits often combine to make this chemistry the most cost effective in severe environment applications. The primary benefits include extended life, higher temperature operation, reduced maintenance and downtime, lower energy consumption, reduced smoke and disposal, and biodegradability.
Is the bold text the answer that what you were looking for?
[ February 17, 2004, 02:08 AM: Message edited by: Jelly ]