The oxidation resistance is extra-powerful, low volatility, acidic material’s quantity produced are less, even under high temperature will not easily generate carbon or rubber/paint, product will not easily accumulate dirt when deteriorating. Its high temperature stability and detergent performance is excellent, Superelevation lubricating. The vapor character is low, on the surface of two types of metal is easy to absorb Polar molecule so to generate protective film.

 

The American Petroleum Institute (API) sets minimum for performance standards for lubricants. Motor oil is used for the lubrication, cooling, and cleaning of internal combustion engines. Motor oil may be composed of a lubricant base stock only in the case of non-detergent oil, or a lubricant base stock plus additives to improve the oil's detergency, extreme pressure performance, and ability to inhibit corrosion of engine parts. Lubricant base stocks are categorized into five groups by the API. Group I base stocks are composed of fractionally distilled petroleum which is further refined with solvent extraction processes to improve certain properties such as oxidation resistance and to remove wax. Group II base stocks are composed of fractionally distilled petroleum that has been hydrocracked to further refine and purify it. Group III base stocks have similar characteristics to Group II base stocks, except that Group III base stocks have higher viscosity indexes. Group III base stocks are produced by further hydrocracking of Group II base stocks, or of hydroisomerized slack wax, (a byproduct of the dewaxing process). Group IV base stock are polyalphaolefins (PAOs). Group V is a catch-all group for any base stock not described by Groups I to IV. Examples of group V base stocks include polyol esters, polyalkylene glycols (PAG oils), and perfluoropolyalkylethers (PFPAEs). Groups I and II are commonly referred to as mineral oils, group III is typically referred to as synthetic (except in Germany and Japan, where they must not be called synthetic) and group IV is a synthetic oil. Group V base oils are so diverse that there is no catch-all description.

Polyol ester basestocks have several excellent performance properties, including thermal stability, super-high VI and fire resistance. Of the base oils mentioned in this column, it is probably the best choice for very high-temperature applications. The two most common applications for polyol ester are fire-resistant hydraulic fluids and jet engine oils. They can be used in engine oils and compressor applications, as well. The negative attributes are the same as those for diester.

Base oils made with the Iso-DeWaxing process are called Group II, and are significantly more pure and have higher performance than Group I base oils. Chevron Delo 400, Mobil Delvac 1300, and Shell Rotella are made from pure Group II oils. Motor oils made with Group-II base oils leave far fewer wax and tar deposits in your engine, and have much better low and high temperature performance than Group I oils. The resulting oils are roughly 97% good stuff (oil) and 3% bad stuff (paraffin and wax). We just cut that 12" dinner candle down to about 2½".

The high and low temperature performance of oils are described by the Viscosity Index. The VI tells us how much the oil thins out as it gets hot. Oils with higher VIs maintain their viscosity better at high temperatures. If the VI is 90 to 100, we call it Group II; if it's refined to a VI of 110 to 115 we call it Group IIa. In the late '90s, an even more involved process was invented yielding base oils with VIs over 120. These base oils are called Group III or "unconventional base oils." The higher the VI, the fewer additives are necessary to achieve the required viscosity. For example fewer additives are needed to turn a Group III base oil into 10w-40 than are required for Group II base oils. Group III oils have essentially no paraffin and wax in them, at least as compared to the 12" dinner candle per gallon in Group I oils.

Group III oils have properties approaching or equaling synthetics, so long as the temperature is above about 40°. Group III based oils are often claimed to not perform as well as synthetics in a couple ways: their low temperature performance is not nearly as good, it is sometimes claimed on the basis of the "ball bearing test" that they offer lower impact resistance, and since their flash point is slightly lower it is claimed that they burn off more easily. However, most modern engines are water-cooled, so it's hard to see how the slightly better flash points of the synthetics ever come into play. I personally don't make a habit of dropping a handful of ball bearing into my oil pan, so I'm not completely clear on what the impact tests mean to me. The low temperature performance of the Group III oils can be improved enormously by blending in a relatively small amount of synthetic base stock and other additives.

Since about 2000, it has become possible at moderate extra cost to process Group II and Group III oils so that their performance below 32° nearly matches the performance of traditional synthetics. Because of this, the oil companies found they could now produce relatively inexpensive 5w-30 and 0w-20 oils. Car companies were quick to see that such oils would help reduce the fuel consumption of their vehicles by a percent or so, which is important as Detroit finds themselves selling more trucks than cars. So, these "fuel-efficient" oils are quickly becoming the factory recommendation in most cars. It's not at all clear that these new low- viscosity oils lead to the longest engine life, but it is clear that these oils help the car companies meet their CAFE federally- mandated fuel economy standards.

In the late 1990s, Castrol started selling an oil made from Group III base oil and called it SynTec Full Synthetic. Mobil sued Castrol, asserting that this oil was not synthetic, but simply a highly refined petroleum oil, and therefore it was false advertising to call it synthetic. In 1999, Mobil lost their lawsuit. It was decided that the word "synthetic" was a marketing term and referred to properties, not to production methods or ingredients. Castrol continues to make SynTec out of Group III base oils, that is highly purified mineral oil with most all of the cockroach bits removed.

Shortly after Mobil lost their lawsuit, most oil companies started reformulating their synthetic oils to use Group III base stocks instead of PAOs or diester stocks as their primary component. Most of the "synthetic oil" you can buy today is actually mostly made of this highly-distilled and purified dino-juice called Group III oil. Group III base oils cost about half as much as the synthetics. By using a blend of mostly Group III oils and a smaller amount of "true" synthetics, the oil companies can produce a product that has nearly the same properties as the "true" synthetics, and nearly the same cost as the Group III oil. The much more expensive traditional synthetics are now available in their pure forms only in more expensive and harder to obtain oils. To the best of my knowledge, Delvac-1, AMSOil, Redline, and Motul 5100 are the only oils made from pure traditional synthetics

The term "polyol esters" is short for neopentyl polyol esters which are made by reacting monobasic fatty acids with polyhedric alcohols having a "neopentyl" structure. The unique feature of the neopentyl structure of polyol alcohols molecules is the fact that there are no hydrogens on the beta-carbon. Since this "beta-hydrogen" is the first site of thermal attack on diesters, eliminating this site substantially elevates the thermal stability of polyol esters and allows them to be used at much higher temperatures. In addition, polyol esters usually have more ester groups than the diesters and this added polarity further reduces volatility and enhances the lubricity characteristics while retaining all the other desirable properties inherent with diesters. This makes polyol esters ideally suited for the higher temperature applications where the performance of diesters and PAOs begin to fade.

Like diesters, many different acids and alcohols are available for manufacturing polyol esters and indeed an even greater number of permutations are possible due to the multiple ester linkages. Unlike diesters, polyol esters (POEs) are named after the alcohol instead of the acid and the acids are often represented by their carbon chain length. For example, a polyol ester made by reacting a mixture of nC8 and nC10 fatty acids with trimethylolpropane would be referred to as a "TMP" ester and represented as TMP C8C10. The following is a list of the more commonly used raw materials for making polyol esters:

POLYOL ESTERS AND AVAILABLE ACIDS Common Alcohols # of Ester Groups Family Available Acids Neopentyl Glycol 2 NPG Valeric (nC5) Isopentanoic (iC5) Hexanoic (nC6) Heptanoic (nC7) Octanoic (nC8) Isooctanoic (iC8) 2-Ethylhexanoic (2EH) Pelargonic (nC9) Isononanoic (iC9) Decanoic (nC10) Trimethylolpropane 3 TMP Pentaerythritol 4 PE DiPentaerythritol 6 DiPE

Each of the alcohols shown above have no beta-hydrogens and differ primarily in the number of hydroxyl groups they contain for reaction with the fatty acids. The difference in ester properties as they relate to the alcohols are primarily those related to molecular weight such as viscosity, pour point, flash point, and volatility. The versatility in designing these fluids is mainly related to the selection and mix of the acids esterified onto the alcohols.

The normal or linear acids all contribute similar performance properties with the physicals being influenced by their carbon chain length or molecular weight. For example, lighter acids such as valeric may be desirable for reducing low temperature viscosity on the higher alcohols, or the same purpose can be achieved by esterifying longer acids onto the shorter alcohols. While the properties of the normal acids are mainly related to the chain length, there are some more subtle differences among them which can allow the formulator to vary such properties as oxidative stability and lubricity.

Branched acids add a new dimension since the length, location, and number of branches all impact the performance of the final ester. For example, a branch incorporated near the acid group may help to hinder hydrolysis while multiple branches may be useful for building viscosity, improving low temperature flow, and enhancing oxidative stability and cleanliness. The versatility of polyol esters is best understood when one considers that multiple acids are usually co-esterified with the polyol alcohol allowing the ester engineer to control multiple properties in a single ester. Indeed single acids are rarely used in polyol esters because of the enchanced properties that can be obtained through co-esterification.

Polyol esters can extend the high temperature operating range of a lubricant by as much as 50 - 100°C 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.

The major application for polyol esters is jet engine lubricants where they have been used exclusively for more than 30 years. In this application, the oil is expected to flow at -54°C, pump readily at -40°C, and withstand sump temperature approaching 200°C with drain intervals measured in years. Only polyol esters have been found to satisfy this demanding application and incorporating even small amounts of diesters or PAOs will cause the lubricant to fail vital specifications.

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 industrial markets polyol esters are used extensively in synthetic refrigeration lubricants due to their miscibility with non-chlorine refrigerants. They are also widely used in a variety of very high temperature applications such as industrial oven chains, tenter frames, stationary turbine engines, high temperature grease, fire resistant transformer coolants, fire resistant hydraulic fluids, and textile lubricants.

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 biodegradability.

Synthetic lubricants were first synthesized, or man-made, in significant quantities as replacements for mineral lubricants (and fuels) by German scientists in the late 1930s and early 1940s because of their lack of sufficient quantities of crude for their (primarily military) needs. A significant factor in its gain in popularity was the ability of synthetic-based lubricants to remain fluid in the sub-zero temperatures of the Eastern front in wintertime, temperatures which caused petroleum-based lubricants to solidify due to their higher wax content. The use of synthetic lubricants widened through the 1950s and 1960s due to a property at the other end of the temperature spectrum, the ability to lubricate aviation engines at temperatures that caused mineral-based lubricants to break down. In the mid 1970s, synthetic motor oils were formulated and commercially applied for the first time in automotive applications. The same SAE system for designating motor oil viscosity also applies to synthetic oils.

Instead of making motor oil with the conventional petroleum base, "true" synthetic oil base stocks are artificially synthesized. Synthetic oils are derived from either Group III mineral base oils, Group IV, or Group V non-mineral bases. True synthetics include classes of lubricants like synthetic esters as well as "others" like GTL (Methane Gas-to-Liquid) (Group V) and polyalpha-olefins (Group IV). Higher purity and therefore better property control theoretically means synthetic oil has good mechanical properties at extremes of high and low temperatures. The molecules are made large and "soft" enough to retain good viscosity at higher temperatures, yet branched molecular structures interfere with solidification and therefore allow flow at lower temperatures. Thus, although the viscosity still decreases as temperature increases, these synthetic motor oils have a much improved viscosity index over the traditional petroleum base. Their specially designed properties allow a wider temperature range at higher and lower temperatures and often include a lower pour point. With their improved viscosity index, true synthetic oils need little or no viscosity index improvers, which are the oil components most vulnerable to thermal and mechanical degradation as the oil ages, and thus they do not degrade as quickly as traditional motor oils. However, they still fill up with particulate matter, although at a lower rate compared to conventional oils, and the oil filter still fills and clogs up over time. So, periodic oil and filter changes should still be done with synthetic oil; but some synthetic oil suppliers suggest that the intervals between oil changes can be longer, sometimes as long as 16,000-24,000 km (10,000–15,000 mi).

With improved efficiency, synthetic lubricants are designed to make wear and tear on gears far less than with petroleum-based lubricants, reduce the incidence of oil oxidation and sludge formation, and allow for "long life" extended drain intervals. Today, synthetic lubricants are available for use in modern automobiles on nearly all lubricated components, potentially with superior performance and longevity as compared to non-synthetic alternatives. Some tests[citation needed] have shown that fully synthetic oil is superior to conventional oil in many respects, providing better engine protection, performance, and better flow in cold starts than petroleum-based motor oil.

 

Synthetic oils were originally designed for the purpose of having a very pure base oil with excellent properties. By starting from scratch and building up your oil molecules from little pieces, you can pretty much guarantee that every molecule in the oil is just like every other molecule, and therefore the properties are exactly what you designed in, not compromised by impurities from dead cockroach shells or whatever. Synthetics were thus originally a reaction to the relatively poor refining processes available from about 1930 to about 1990. The original synthetics were designed for the Army Air Force in WW II. They simply could not make their high- performance turbo-charged radial engines stay alive on the available motor oils of the time.

One process for making synthetic base oils is to start with a chemical called an olefin, and make new molecules by attaching them to each other in long chains, hence "poly." The primary advantage of Poly-Alpha-Olefin "PAO" base oil is that all the molecules in the base oil are pretty much identical, so it's easy to get the base oil to behave exactly as you like. PAOs are called Group IV base oils.

Until about 2000, these PAO base oils had an enormous advantage over mineral base oils in low temperature performance and in resistance to oxidation, which is critical in keeping the oil from forming acids. However, modern group-III oils can nearly match the performance of PAOs at about half the price. Because of this, PAO based oils are rapidly disappearing. There are new processes being investigated which may significantly cut the cost of producing PAOs, and make them an important component of oil again.

Another type of base oil is made from refined and processed esters and is called Group V. Esters start life as fatty acids in plants and animals, which are then chemically combined into esters, diesters, and polyesters. Your vegetarian girlfriend should love that. Group V base stocks are the most expensive of all to produce. However, the esters are polar molecules and have very significant solvent properties - an ester base oil all by itself will do a very decent job of keeping your engine clean. So, people who are serious about making a superior oil will usually mix some Group V oils into their base stock.

PolyEster oils have by far the best performance in extreme high temperatures, and are the preferred oil in old "air- cooled" Nortons. I put "air-cooled" in parenthesis as one could also call these engines "prayer- cooled." The Norton 750 commando will destroy a Group I oil fill in 75 miles on a 100 degree day. No kidding. The Brits really did not understand until about 1990 that some of us live in places where the temperatures get over 80 degrees and cities are more than 10 miles apart. If you love those old British twins, you need to find a good supply for oil.

Finally, there are new chemicals emerging which are made from liquefied natural gas called GTL (gas to liquid) base oils. These will be called Group III+, and many people think they will become an important part of the oils you buy by 2010. These GTL base oils have natural VIs of 140 or more, meaning for most applications they won't require any VII package at all. Natural gas is primarily made up of only one type of molecule, so the refining is already done for you. Most oil wells throw off a lot of natural gas. In many cases, it's more expensive to transport this gas to a large city than the gas is worth, so it's just burned off. For example, Iran burns off enough natural gas each day to power their entire country, electricity, cars, ships, airplanes, the whole thing. So the next time you hear Iran's nuclear reactors are purely for peaceful production of energy, you can wonder like the rest of us why a country that burns off more than their entire energy needs must spend tens of billions of dollars developing alternative energy sources. Well, anyway, natural gas is a chemical looking for a use. All you have to do is chemically attach these molecules to each other to turn them into quite pure oil stocks.

"Semi-synthetics" are oils which are a blend of petroleum oil and no more than 30% synthetic oil. If the manufacturer adds no more than 30% synthetic oil and does not change the additive package, they do not have to recertify the oil. These days, since everyone has agreed that Group III base oils are "synthetic," I'm not sure "semi-synthetic" means anything at all. The manufacturers love this stuff: it costs about 15% more to make the oil, and they get to charge about double. I don't recommend semi-synthetics. Save your money and take your kids to McDonalds.

Diesters, or dibasic acid esters, were developed during World War II and are the reaction product of long-chain alcohols and carboxylic acids. Historically, they have been effective as reciprocating compressor lubricants due to their low coking tendency at temperatures of 400°F or higher. They also provide excellent solvency and detergency. The aggressiveness of diesters toward elastomers, seals and hoses has limited the usefulness of these fluids. Newer fluids, such as polyol esters, meet the needs of many applications formerly filled by diesters.

Polyol esters, or Neopentyl poly esters, have largely replaced diesters in high-temperature applications where oxidative stability is critical. Common applications include their use as lubricants in aircraft engines, high-temperature gas turbines, hydraulic fluids, and as heat exchange fluids. They can also be used as a co-blended basestock with PAOs to enhance additive solubility and reduce the tendency of PAOs to shrink and harden elastomers.

PAOs are hydrocarbon polymers manufactured by the catalytic oligomerization of linear alpha olefins like alpha-decene. They are considered high-performance lubricants and provide a high viscosity index and hydrolytic stability. PAOs are the most commonly used, and are generally less expensive than other synthetic lubricants. They have been used in passenger car motor oils, as well as numerous industrial lubricant applications.

 

via:Noria Corporation

Hmmm. That’s a tough question. The answer is not as simple as “yes” or “no”. A better question would be: Is synthetic oil the best choice for this application? All types of synthetic base oils can be the best choice for certain situations. The trick is identifying those situations where they make sense or provide value.

There are plenty of potential benefits to using synthetic oil vs. mineral oil, but that doesn’t mean that synthetics are necessarily better. In order to get value from using a higher-priced synthetic oil, you must ensure that you are utilizing the potential improved performance of those products; and to make those determinations, you need to understand the conditions that allow synthetics to provide that value.

To more fully understand this issue, first consider the major advantages of common types of synthetic base oils and then identify the conditions for which these advantages become benefits.

For the sake of brevity, I will not discuss all synthetics, but rather focus on the most common ones – PAOs (polyalphaolefins), PAGs (polyalkaline glycol), diester and polyol ester.

 

Polyalphaolefins (PAOs)

PAOs, often called synthetic hydrocarbons, are probably the most common type of synthetic base oil used today. They are moderately priced, provide excellent performance and have few negative attributes.

PAO base oil is actually similar to mineral oil. The advantage comes from the fact that it is built, rather than extracted and modified, making it more pure. Practically all of the oil molecules are the same shape and size and are completely saturated.

The potential benefits of PAOs are improved oxidative and thermal stability, excellent demulsibility and hydrolytic stability, a high VI, and very low pour point. Most of the properties make PAOs a good selection for temperature extremes – both high operating temperatures and low start-up temperatures. In my opinion, those are the conditions that favor PAO selection. Typical applications for PAOs are engine oils, gear oils and compressor oils.

The negative attributes of PAOs are the price and poor solubility. The low inherent solubility of PAOs creates problems for formulators when it comes to dissolving additives. Likewise, PAOs cannot suspend potential varnish-forming degradation by-products, although they are less prone to create such material.

For the most part, this issue of solubility can be addressed through the addition of other base oils such as diester. The cost issue is really about whether or not you actually get value by utilizing the performance.Polyalkaline glycols (PAGs or PGs)

PAG base oils have several unique properties that allow them to work very well in certain applications. In general, they have excellent oxidative and thermal stability, very high VI, excellent film strength and an extremely low tendency to leave deposits on machine surfaces. The low deposit-forming tendency is really due to two properties – the oil’s ability to dissolve deposits and the fact that the oil burns clean. So when they are exposed to a very hot surface or subjected to micro-dieseling by entrained air, PAGs are less likely to leave residue that will form deposits. PAGs may also be the only type of base oil with significantly lower fluid friction, which may allow for energy savings. The other unique property of PAGs is the ability to absorb a great deal of water and maintain lubricity.

There are actually two different types of PAGs – one demulisifies and the other absorbs water. The latter can be very useful if you have a compressor that cannot be stopped that is continually contaminated with large amounts of water. The most common applications for PAGs are compressors and critical gearing applications.

The negatives of PAGs are their very high cost and the potential to be somewhat hydrolytically unstable.

 

Dibasic Acid Ester (Diester)

The properties of diester are somewhat similar to that of PGs. It has excellent oxidative and thermal stability, very high VI and excellent solubility. This excellent solubility makes it a good choice for reciprocating compressors, where valve deposits can be a huge problem. Another common application for diester is in synthetic engine oil. It is often used as an additive with PAO basestocks to provide the necessary solvency for the engine oil’s large additive package. As a side effect, the synthetic engine oil will have excellent detergency. The negative attributes of diester are the high price and poor hydrolytic stability.

Polyol Ester

Polyol ester basestocks have several excellent performance properties, including thermal stability, super-high VI and fire resistance. Of the base oils mentioned in this column, it is probably the best choice for very high-temperature applications. The two most common applications for polyol ester are fire-resistant hydraulic fluids and jet engine oils. They can be used in engine oils and compressor applications, as well. The negative attributes are the same as those for diester.

 

Go for ‘Right’ Quality

There are many applications for which synthetic oils provide solutions to tough operating conditions. I have mentioned a few of those here, but there are others. To me, it is not so important to use the “best” quality lubricant in every application, but rather to use the “right” quality.

Many people waste money on expensive products that for a number of reasons don’t improve reliability or anything else. One other important thing to remember is that I am discussing the properties of base oils, not finished lubricants. It is quite possible for a finished lubricant using a mineral basestock to offer better performance than a similar product utilizing a synthetic.

So, back to the original question, is synthetic oil better? The answer is yes … and no … or maybe. You’ll have to decide.