PAO vs Ester

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Jul 18, 2002
I would consider PAO synthetics to be the norm for most big name synthetics (the real synthetics) and it has been proven that they are suitable for long term use in an engine. It seems to me that Esters are used mostly by smaller players and niche (racing) companies and I know very little about them. What are the pros and cons of PAO's vs esters? Are esters better, but more expensive or are PAO's better? Has it been established that the ester synthetics can be used for 100K, 200K or more miles without causing a problem? I've heard the PAO's were problematic until they got the formula perfected. Thanks, Jon
I should add that the main reason for this post is that I think Redline oil is interesting, but I can't figure out how good it is for regular consumer use. I've seen very little oil analysis for Redline - I think Bror Jace's is the only one I've seen. His weren't overly impressive, but they may have been complicated by a coolant leak. Jon
I don't believe there are any synthetic out there that only use one of these two, I think that all of them use a combination of the two. Some just have a higher concentration of one or the other. One thing I do know is that PAOs by themselves have a tendancy to shrink seals, while esters will swell them, which is why you probably won't find a 100% PAO base. They need the esters in there to counteract the PAO seal shrinkage. Someone correct me if I'm wrong. [Smile]
In general Esters are a slightly better lubricant and have a higher operating limit. I believe they tend to cling to metal a little better than PAO's. PAO's are not quite as affected by moisture and also are more compatable with mineral oils. Also Esters tend to be better with additive solubility. Thats not very technical, but the best I can do. Others may be able to correct/clarify or refute this info. [I dont know]
Motul is the only large (very large) company using esters extensively. You might want to call their tech guy in CA and talk to him. I did about a year ago and he was very friendly and helpful. He also told me about their complex esters that were so expensive that only the full-factory race teams get them.
CVL: "Motul is the only large (very large) company using esters extensively." OK, so when you say large, you are excluding Red Line, Synergen and most other specialty oil brands? [Confused] --- Bror Jace
PAO's and Esters are both wonderful lubricants, each with their individual strengths and weaknesses as they relate to applications. Both exhibit broad range temperature viscosity stability, extremely high film strength, high heat transfer rates etc. The negative aspects for Esters as they relate for use as an automotive engine lubricant are: 1. Esters have viscosity limitations: there is a production/cost limitation for making an oil in the 30 and 40 weight range. 2. Esters are hygroscopic. i.e. esters have great natural detergency/reactivity and likewise, love water. This affinity for water is why ester based lubricants are shipped in steel drums. If shipped in plastic they would absorb water like a sponge and will be unusable as a lubricant. In many ester lubricants, after they have been removed from their container and go through two pours, they are rendered useless as they contain too much water to be used in certain applications. 3. Esters are generally much more expensive than PAO's. So, given deficiency #2 combined withi #3 and it is easy to see why esters are not used as engine lubricants. Some early synthetic engine oils were ester based and in short order turned engine internals into rusting hulks. Plus due to deficiency #1, were thinner viscosities and did in fact leak horribly, providing the basis for the myth that "synthetic oils are thin like water'. The first ester engine oils were indeed water level viscosities! That said, Esters work just great as turbine engine lubricants. With a 38,000 rpm engine, light viscosity is perfect, working in a closed, hot environment keeping the water out and all the good ester properties of film strength, etc. are right on target.. And yes, all jet oils are packaged in old fashioned metal quart cans.. Most jet oils go 20,000 to 30,000 hours between changes!
Motul is bigger than Redline or Synergen. [Duh!] If you read the original post, the poster stated that esters seemed to be used mostly by smaller players and niche (racing) companies. Motul is the largest company that seems to use esters extensively through much of their lineup.
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