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Synthetic Oils

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 (RedLine) 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 RedLine 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.

As you can see in the table above, synthetics offer real advantages when your engine is very cold and when your engine is very hot. The viscosity numbers shown above are at 212°F. At 32°F the PAOs and Diesters have about one third the viscosity of the mineral oils, meaning they pump through your engine three times better. Since about 75% of all the wear on your engine happens in the first five minutes after you start it up, synthetics offer an advantage in significantly reducing engine wear.