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To be honest, I don't exactly know the difference between PAO and Esters.
Hi FD777
PAO molecules are constructed solely from Hydrogen and Carbon atoms, hence the term "Hydrocarbons". But they are much different from mineral oil.
Mineral oils are also hydrocarbons, but they are mixtures of literally thousands of different hydrocarbon molecules in all different shapes and sizes, extracted from crude oil. Some of the hydrocarbons in mineral oil are very strong and make excellent lubricants, and some are weak and make poor lubricants.
A famous sculpture was once asked "How can you make a statue of a beautiful woman from an ugly slab of marble", and he said: "It's easy, you just chip away everything that doesn't look like a beautiful woman".
The same is true in making a good base oil from crude - you just "chip" away everything that does not look like a good oil. Unfortunately, it is not economically feasible to remove ALL of the weak molecules from crude oil, and the remaining "weak links" limit the high temperature stability and low temperature fluidity of the oil. Hence mineral base oils are always a compromise of cost and performance.
The best molecules in mineral oil for lubrication are the branched saturated hydrocarbons. So to make a better base oil, it would be nice to use only these strong molecules and leave out the weak ones. That is what PAOs do. The whole concept of “synthetics” is that you start by defining the best molecules for the job, then build these molecules – and only these molecules – from pure chemical building blocks. You don’t have to worry about removing the weak components because they were not part of the design and are not present. PAOs are built up from pure “1-decenes” (hydrocarbons) and the resulting product is the nice pure branched saturated hydrocarbons that we covet.
Esters are made by reacting acids and alcohols. These are not the kind you may be familiar with – the alcohols are usually solids (not the drinking sort!) and the acids don’t burn your skin (at least not too much!). Like with PAOs, one custom designs the molecules for the job and builds them from pure chemical building blocks, but in this case the resulting product is synthetic hydrocarbons with some oxygen atoms attached. These oxygens make the molecules “polar”, sort or like magnetically charged PAOs. This polarity adds some nice properties that are especially useful at high temperatures, such as lower volatility, better oxidative stability, higher lubricity, better solubility, biodegradability, and cleanliness. On the downside, esters cost considerably more than PAOs. You can get more details if interested from our website
Hatco in the About Esters paper.
For moderate temperature applications such as motor oils and many industrial uses, PAOs or PAO/ester blends are the premium base oils for maximum efficiency as they can extend drains, reduce maintenance, and save fuel/energy. For very high temperature applications such as jet engines and industrial ovens, esters are generally used alone, especially the polyol (POE) type.
Sorry, there I go again with a long post. Maybe I should just write a book and get it over with.
Tom
