Somewhat applicable to the discussion at hand, I just had one of my customers who tracks his Vette give me his used oil analysis report after 5,000 miles and 5 months of use which included one full track day at Watkins Glen:
Corvette C5 Used Oil Analysis Report – AMSOIL SAE Synthetic 10w30
Quote:
Originally Posted by Route 66
In the long haul...oil is oil....all mineral based.
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Not true.
The API has not come out and defined the term "synthetic" but rather classified oils into groups.
Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils use these stocks, they are generally used in less demanding applications.
Group II base oils are common in mineral based motor oils. They have fair to good performance in the areas of volatility, oxidation stability, wear prevention and flash/fire points. They have only fair performance in areas such as pour point and cold crank viscosity. Group II base stocks are what the majority of engine oils are made from. 3000 mile oil changes are the norm.
Group III base oils are subjected to the highest level of refining of all the mineral oil stocks. Although not chemically engineered, they offer improved performance in a wide range of areas as well as good molecular uniformity and stability. By definition they are considered a synthesized material and can be used in the production of synthetic and semi-synthetic lubricants. Group III is used in the vast majority of full synthetics or synthetic blends. They are superior to group I and II oils but still have limitations. Some formulations are designed for extended oil changes.
AMSOIL XL Motor Oils, Castrol Syntec and many others fall into this category.
Group IV are polyalphaolefins (PAO) which are a chemically engineered synthesized basestocks. PAOs offer excellent stability, molecular uniformity and performance over a wide range of lubricating properties.
AMSOIL SAE Synthetic Motor Oils and Mobil 1 primarily use group IV basestocks. PAO is a much more expensive basestock than the highly refined petroleum oil basestock of Group III.
Group V base oils are also chemically engineered stocks that do not full into any of the categories previously mentioned. Typical examples of group V stocks are Esters, polyglycols and silicone. Redline uses an ester basestock.
In the 90s, Mobil filed suit against Castrol for falsely advertising Syntec oil as synthetic, when in fact it contained a Group III, highly hydroprocessed mineral (Dino) oil, instead of a chemically synthesized (group IV or V) basestock. Due to the amount that the mineral oil had been chemically changed, the judge decided in Castrol's favor. As a result, any oil containing this highly hydroprocessed mineral (Dino) oil (currently called Group III basestock by the American Petroleum Institute) can be marketed as a synthetic oil. Since the original synthetic basestock (polyalphaolefin or PAO) is much more expensive than the Group III basestock, most of the oil blenders switched to the Group III basestock, which significantly increased their profit margins.
Here is a description of Group V and IV synthesized basestocks I found on another forum. Gives a good background into esters and PAOs.
"Esters: Diesters (dibasic acid esters)
During World War II a range of synthetic oils was developed. Among these, esters of long-chain alcohols and acids proved to be excellent for low temperature lubricants. Following World War II, the further development of esters was closely linked to the aviation gas turbine. In the early 1960s, neopolyol esters were used in this application because of their low volatilities, high flash points and good thermal stabilities.
Diesters are prepared by reacting a dibasic acid with an alcohol containing one reactive hydroxyl group. Note that the hydrolytic stability of diesters is not as good as mineral oils. Hydrolytic stability refers to how the lubricant reacts in the presence of water. Hydrolytic degradation can lead to acidic products, which, in turn, promote corrosion. Plus, hydrolysis can also materially change the chemical properties of the base fluid, making it unsuitable for the intended use. Systems that can contract high levels of moisture include systems that operate at low temperatures or that cycle between high and low temperatures and also certain fuels such as racing engines running alcohol, which has a cooling effect in the engine. Racing engines using ester based lubricants should have the lubricant changed regularly.
Diesters have good lubricating properties, good thermal and shear stability, high viscosity indexes and have exceptional solvency and detergency. Diesters are superior fluids for aircraft engines and compressors, although mainly older jet aircraft. Diesters are also used as a base oil or part of a base oil for automotive engine oils and in some low temperature greases (note: modern military and commercial jet aircraft almost universally use lubricants formulated with polyol esters as the base fluid now).
Diesters are incompatible with some sealing materials and can cause more seal swelling than mineral oils. The scientific reason for this is as follows: diesters have a low molecular weight that results in low viscosities. This combined with their high polarities makes them quite aggressive to elastomeric seals. This can be reduced by using better elastomers or by carefully blending with PAOs to nullify their swelling effects, since PAO base stocks are nonpolar.
Esters: Polyolesters (Neopentyl Poly Esters)
Polyol esters are formed by reacting an alcohol with two or more reactive hydroxyl groups. These fluids are used primarily for aircraft engines, high temperature gas turbines, hydraulic fluids and heat exchange fluids. Polyol esters are much more expensive than diesters. Lubricating greases with polyol esters as the base fluid are particularly suited to high temperature applications. Polyol esters have the same advantages/disadvantages as diesters. They are, however, much more stable and tend to be used instead of diesters where temperature stability is important. In general, a polyol ester is thought to be 40-50 deg. C. more thermally stable than a diester of the same viscosity. Esters give much lower coefficients of friction than those of PAO and mineral oil. By adding 5-10% of an ester to a PAO or mineral oil the oils coefficient of friction can be reduced markedly.
Polymerized alpha olefin: Polyalphaolefin, Olefin Polymers, Olefin Oligomers- a synthetic hydrocarbon
PAOs are commonly used to designate olefin oligomers and olefin polymers. The term PAO was first used by Gulf Oil Company (later acquired by Chevron), but it has now become an accepted generic term for hydrocarbons manufactured by the catalytic oligomerization of linear alpha olefins having six or more carbon atoms. PAOs are gaining rapid acceptance as high-performance lubricants and functional fluids because they exhibit certain inherent and highly desirable characteristics. These favorable properties include:
A wide operational temperature range.
Good viscometrics (high viscosity index).
Thermal Stability.
Oxidative Stability.
Hydrolytic stability. *
Shear stability.
Low corrosivity.
Compatibility with mineral oils.
Compatibility with various materials of construction.
Low toxicity.
Manufacturing flexibility that allows tailoring products to specific end-use application requirements.
* Of particular interest in relation to demonstrating superior hydrolytic stability of PAO fluids is a test that was conducted to find a replacement for a silicate ester based aircraft coolant/dielectric fluid used by the U.S. military in aircraft radar systems. The test method required treating the fluids with 0.1% water and maintaining the fluid at 170 or 250 deg. F. for up to 250 hours. Samples were withdrawn at 20- hour intervals, and the flash points were measured by the closed cup method. A decrease in flash point was interpreted as being indicative of hydrolytic breakdown to form lower-molecular-weight products. The PAO showed no decrease in flash point in any of the test conditions, while the silicate ester based fluid showed marked decreases. The PAO fluid maintained started out with a flash point of 300 deg. F. and only dropped to 295 deg. F. at 80 hours into the test, while the silicate ester fluid, which started out with a flash point of 270 deg. F., ended up with a flash point of 220 deg. F. at only 55 hours into the test.
PAOs are used extensively as automotive lubricants (engine, gear, transmission, grease, hydraulic). PAOs are also super premium oils for automotive applications operating in temperature extremes. PAOs are a synthetic hydrocarbon that is compatible with mineral oils. In industrial applications, they may be combined with organic esters to be used in high temperature gear and bearing oils, as well as gas turbines. They are also used as a base fluid in some wide temperature range greases.
The general manufacturing process used to form PAOs is performed by combining a low molecular weight material, usually ethylene gas, into a specific olefin which is oligomerized into a lubricating oil material and then hydrogen stabilized. There are a variety of basic building block molecules used to form the finished lubricant, which are dependent on the range of requirements of the specific lubricant.
Seal compatibility is an important factor for any lubricant. Unlike mineral oils, PAO does not have a tendency to swell elastomeric materials. Early commercial PAO products were not formulated properly to allow for this difference in behavior. Consequently, early PAOs gained an undeserved reputation for leakage. Extensive tests have since shown that the addition of small quantities of an ester to the formulation easily alleviates this problem.
Recent work has indicated that the proper choice of other performance additives may eliminate the need to employ esters, but this approach is not yet in practice for crankcase applications. In a test of a PAO vs. a mineral oil for seal compatibility, four seal materials were studied: acrylate, silicone, nitrile and fluoroelastomer. The seals were evaluated at the end of the test for changes in tensile strength, elongation, volume (seal swell), and hardness. The PAO performance fell within the specification limits for all four elastomers. The mineral oil failed with silicone. Similar tests have been carried out with fully formulated part- and full-synthetic PAO oils. In all cases the fluids met the specifications.
Recent data shows that PAO-based fluids provide superior performance for the high-tech cars and trucks being built today. Todays engines are smaller and more demanding and operate at higher RPMs and under hood spaces is limited which causes increased operating temperatures. Both the thermal conductivity and heat capacity of PAO fluids are about 10% higher than values for comparable mineral oils. The net result is that PAO-lubricated equipment tends to run cooler.
Summary
There is clearly no doubt that synthetic lubricants are superior to petroleum based oils. An excellent summary of in-depth studies that were conducted on the benefits of synthetic lubricants is presented in Appendix B of the Society for Automotive Engineers, Progress in Technology ****** 22 and was conducted during the 1970s and 1980s. The nine superior performance features of synthetic engine oils that were documented by extensive laboratory and field testing are listed below:
Nine Superior Performance Features of Synthetic Engine Oils
Engine Cleanliness.
Improved Fuel Economy (4.2% average increase)
Oil Economy (lower consumption)
Excellent Cold Starting and Low Temperature Fluidity
Outstanding Performance in Extended Oil Drain Field Service
High Temperature Oxidation Resistance
Outstanding Single and Double Length SAE-ASTM API SE and SF Performance Tests (note SE and SF specs were the latest at the time of the testing)
Excellent Wear Protection
Extended drain capability for heavy-duty diesel trucks and gasoline powered trucks. Note: this particular test was based on truck fleet testing, however extended drain capability holds true for passenger cars as well.
These same superior performance features of synthetic engine oils hold true today just as they did when this extensive testing was conducted and has since been verified by many more studies and testing as well as countless millions of miles of field service in every possible type of vehicle and equipment application."
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