AMSOIL Synthetic Lubricants

The Problem With Conventional Petroleum Oil - Resisting Foaming

As oil is splashed around the engine by the rapidly moving engine parts, foaming can occur. Unfortunately, foam is a poor lubricant and a poorer heat exchanger. Therefore, foaming must be kept to a minimum.

Because of the rapidly moving parts in an engine, oil is constantly being mixed with air. This produces foam which is a lot of air bubbles which may or may not readily collapse. These air bubbles normally rise to the surface and break, but water and other contaminants slow this process.

Foam is not a good conductor of heat, and will impair the cooling of the engine parts. Also, foam does not have the ability to carry much of a load, this results in excessive engine wear.

Foam or entrained air bubbles in the oil will under some conditions implode and cause severe pitting of the affected surfaces.

Foam depressant additives are used in the manufacture of automotive lubricants, to reduce the amount of foaming.

The Issues with Petroleum Oils:

Conventional Petroleum Oils do foam fairly easily and especially if they are contaminated. Unfortunately most people never see the amount of foam that sometimes is formed in the crankcase.

Very few Conventional Petroleum oil formulations actually contain the proper amount of anti-foam additives and many do not have any at all.

Vehicle owners with SUV’s on which the front differential is seldom used have many times experienced such severe foaming that the oil leaks out of the breather tubes. This usually happens on vehicles that are seldom operated in the 4x4 mode, and the front differential oil is both oxidized and has absorbed some water.

Foaming can occur at speeds that are too low or too high, as well as when the oil viscosity is either too high or too low. This is also one reason why multi-grade Petroleum oils are used in modern engines.

One factor influencing the cost of oil products you'd never suspect

Buyers are reporting a “perfect storm” of supply and demand issues in the sulfuric acid market that has resulted in a huge jump in sulfuric acid prices. Sulfuric acid prices in March hit a record high of $329/ton according to Purchasingdata.com after trading at $90/ton as recently as October. The increase is being attributed to a combination of factors: rising sulfur prices, increasing demand for sulfuric acid from the fertilizer markets, and short supply of sulfuric acid.

What most people don't realize is that sulfuric acid is a crucial element in the production of gasoline additives.  Sometimes, the structures of molecules in one fraction are rearranged to produce another. Commonly, this is done using a process called alkylation. In alkylation, low molecular weight compounds, such as propylene and butylene, are mixed in the presence of a catalyst such as sulfuric acid (a by-product from removing impurities from many oil products). The products of alkylation are high octane hydrocarbons, which are used in gasoline blends to reduce knocking (see "What does octane mean?" for details).

So as sulfuric acid prices increase, so do the products that contain this ingredient. The U.S. has also seen a shortage in supply of sulfuric acid. The U.S. has imported the majority of sulfuric acid from China in the past, but recently, China has slowed the trade of sulfuric acid to the U.S. because its own demand is greater than what China can produce for both the U.S. and itself.

A February story in the Ames (Iowa) Tribune says “the pricing of sulfuric acid, a manufacturing commodity used in the production of metals and fertilizer, has soared due in part to the increased additional demand from the manufacture of ethanol fuel.”

It isn't just fuel that is affected.  Automotive tier-one supplier Johnson Controls in January raised lead-acid battery prices by 4% and cited a dramatic jump in sulfuric acid prices as one of the reasons.

So, what’s behind the huge price increases? Increased demand for sulfuric acid from booming agricultural and base metals markets has pushed the raw material price of sulfur through the roof in the U.S. while the U.S. market continues to see a long-term slowdown in sulfur supply from reduced production at oil refineries.

The Problem With Conventional Petroleum Oil - Sealing the Combustion Chamber

The piston rings and cylinder walls may look smooth to the naked eye, but they are microscopically rough.

The surfaces of the piston rings, ring grooves, and cylinder walls are not completely smooth. This would become evident under a microscope as small hills and valleys. For this reason, the rings can never prevent high combustion and compression pressures from escaping into the low pressure area of the crankcase. This would result in a reduction of engine power and efficiency

In order to better seal the combustion chamber during the compression and power strokes, a thin film of motor oil must fill in all the little discontinuities. Obviously, it does this in addition to lubricating the contact points between the rings and the cylinder walls.

Motor oil fills in the hills and valleys and greatly improves the seal. Because the oil film is only about 0.001 inches or 0.025 mm thick, it cannot compensate for excessive wear of the rings, ring grooves, or cylinder walls. In a new or rebuilt engine, oil consumption will be relatively high until these surfaces have been smoothed out enough to allow the oil to form a good seal.

The Problem with Petroleum Oil:

Conventional Petroleum Oils do a fairly good job of properly sealing both the pre-ignition compressed gases as well as the high temperature and high-pressure gases burning power stroke burn. The correct viscosity at the operating temperature is however extremely important. The quality of the "seal" is adversely affected both at speeds that are too low or too high, as well as when the oil viscosity is either tool high or too low. This is also one reason why multi-grade Petroleum oils are used in modern engines.

New discovery : Maybe oil isn't from dead dinosaurs...

An article written by Jerome R. Corsi, "New data: Maybe oil isn't from dead dinos" was published recently by WorldNetDaily that indicates that Saturn moon has more hydrocarbons than all of Earth's known reserves.  Researchers have determined that Saturn's moon Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth, according to a team of Johns Hopkins University scientists, adding to evidence that oil is not biological in origin.

The scientists at the Laurel, Md., institution were reporting this week on data collected from NASA's Cassini probe.

"Several hundred lakes or seas have been discovered, of which dozens are estimated to contain more hydrocarbon liquid than the entire known oil and gas reserves on Earth," wrote lead scientist Ralph Lorenz of the university's Applied Physics Laboratory in the  Jan. 29 issue of the Geophysical Research Letters.

Lorenz also reported dark dunes running along the equator cover 20 percent of Titan's surface, comprising a volume of hydrocarbon material several hundred times larger than Earth's coal reserves.

"Titan is just covered in carbon-bearing material – it's a giant factory of organic chemicals," Lorenz wrote.

Lorenz used the term "organic chemicals" in the sense that hydrocarbons are traditionally included within the study of "organic chemistry," not to imply any of the hydrocarbons discovered on Titan are of biological origin.

An Age Old Problem - How to Keep the Engine Cool?

Because only about 60 percent of the engine cooling is handled by the radiator and coolant, the other 40 percent (more in an air-cooled engine) must be taken care of by the engine oil. The combustion process takes place at about 2000°F to 3000°F, which can heat pistons and valves to 1000°F in extreme cases. In pistons, much of this heat travels down the connecting rods and affects the bearings. Since tin and lead, two common bearing materials, soften drastically around 350°F and melt at 450°F and 620°F (respectively), it is important for the oil to transfer excess heat away from the bearings as quickly as possible. In valves, the long, thin valve stem is more easily stretched when hot as the valve spring pulls the valve tight against the seat. Too much stretch, and valve clearances disappear and valves and seats burn.

There are ways of helping the oil keep its cool without resorting to chemistry. Increasing sump capacity increases the length of time the oil gets to cool off before being thrust into the breech again, and the more oil there is the more BTUs it takes to heat it up and keep it hot. Adding an oil cooler allows the oil to more readily lose heat, and can add to the volume of oil in the engine.

Incidentally, installing a high-volume oil pump to cure high oil temperatures actually exacerbates the problem in most engines. A high-volume pump takes more horsepower to run (creating heat), and it over-pressurizes oil passages, which can lead to greater oil consumption as the oil is squirted or flung onto the cylinder walls or past seals.

The Issue with Petroleum Oils:

Conventional Petroleum Oils do not conduct heat too well, and actually most of the increase in oil temperature can be attributed to internal friction in the oil itself as the bulk oil temperature will rise rapidly with engine speed much faster than with engine load.

Typical Motor Oil running temperature is about 20°F higher than the coolant temperature. It is however possible to have oil sump temperature in excess of 300°F even when the coolant is in 220°F to 240°F range. In many Air-cooled engines and especially the very small ones used in generators and lawn equipment it is not unusual to see oil temperatures approaching 400°F.

Conventional Petroleum oil deteriorates rapidly at temperatures over 260°F and at 320°F its useful life is only about two hours !

Burning Cleanly - Why do Synthetics do Better than Conventional Oils

The oil is called upon to lubricate such tricky areas as the cylinder walls and the valve guides and stems, which means that some oil is going to enter the combustion chamber and be burned along with the fuel. If it leaves a residue, piston rings can become stuck, dropping compression and overall engine efficiency.

If the oil leaves metallic deposits when it burns, they can clog the electrode on the spark plug and cause misfiring, which will also drop engine efficiency and accelerate the formation of sludge materials. If the oil leaves behind crystalline or abrasive residue when it burns, cylinder walls and bearing surfaces will be slowly but surely machined away as the sharp-edged crystals circulate through the motor.

Of course, a build-up of black carbon on the head of the piston and on the combustion chamber attracts and absorbs heat to a far greater extent than does a clean metal surface. This extra heat can cause detonation, place a higher demand on the engine's cooling system, and hasten oil break-down.   

The Problem with Petroleum Oils:

Conventional Petroleum Oils that are pure do not cause too many deposits, as they burn relatively cleanly in the combustion process. However modern Petroleum oils like the latest API SM category do contain many chemical additives which will form deposits in engines with high oil consumption.

This is one reason why manufacturers now finally pay attention to oil consumption and why latest engine designs consume "almost" no oil in normal operation.

A Practical Application

Two-cycle engines are simple and have no lubricant distribution system to speak of. In pre-mix engines, oil is added to the fuel, and in injector systems, oil is added to the fuel and air at a rate appropriate to conditions as the fuel and air enter the engine. In either case, the oil is simply mixed with the fuel to lubricate the engine parts.

The reason two-cycle engines work so hard is simple: every stroke is a power stroke. In a four-stroke engine, the piston rises and is driven down by combustion (a power stroke), but the next time the piston rises it simply pushed out exhaust gasses. In two-cycle engines, exhaust gas is driven out by the incoming oil-fuel mixture as the piston forces the mixture into the combustion chamber - on each and every stroke. These factors combine to place tremendous demands on lubricants.

• Must Burn, and burn cleanly
  Since the oil is mixed with the fuel, it must also be burned with the fuel, and burned cleanly. If you've seen the tell-tale blue smoke coming from an outboard boat motor or motorcycle, you've seen a case where oil isn't burning cleanly - environmental regulations, concern for the environment and just plain common sense make that kind of scene unacceptable.
  
  A more subtle danger when oil doesn't burn cleanly is what happens to the engine itself. Deposits in a hard-working two-cycle engine can cause scuffing and ultimately engine failure. Even exhaust outlets can become plugged, and when that happens, engine efficiency drops and wear increases.

• Must Resist volatility
  Two-cycle engines run hot. But while the oil must burn cleanly at combustion temperatures, it must not burn at the hot temperatures found outside the combustion chamber. If an oil is not highly resistant to this volatile evaporation, deposits can begin to form and cause engine damage.

• Must Lubricate
  Two-cycle oils must lubricate effectively under these severe conditions. Failure to lubricate properly can quickly result in excessive wear and finally engine failure.

• Must Assist in cooling
  Two-cycle engines are either air-cooled (hotter) or water-cooled (cooler). In either case, the lubricant must take on a major portion of the cooling duties.

The Problem with Conventional Oil

Conventional petroleum lubricants use bright stock, a heavy cut of petroleum, to add lubricity and anti-scuffing properties. Unfortunately, bright stock doesn't burn cleanly. In addition, petroleum basestocks are more prone than synthetics to volatile evaporation, and when they volatize, they tend to form hard carbon deposits that cause extreme engine damage.

To solve the contamination problems caused by dirty-burning bright stock, conventional two-cycle oil manufacturers use solvents to keep engine parts clean.

When using low-grade solvents, however, there may be drawbacks to this approach. Low-grade solvents help with dispersency, but they can hurt film strength and ultimately detract from lubrication performance, and manufacturers that treat two-cycle oil as a commodity are likely to use bargain-basement solvents instead of more costly ones that perform better.

To meet pumpability, mix ratio and low-temperature fluidity requirements, AMSOIL 2-Cycle Injector Oil uses only high grade solvents, which lead to its superior performance. However, as we'll see, solvents are unnecessary in a high quality pre-mix oil.

Finally, to deal with hotter temperatures, conventional two-cycle oils used in air-cooled applications must employ metal-containing (ash) additives to overcome the weaknesses in their basestocks. Since ashed additive packages can cause fouling problems, these companies then formulate a separate oil for cooler water-cooled applications.

How Do Conventional Petroleum Oils Minimize Friction?

When there is full-film lubrication between all metal parts, the internal friction of the oil becomes a factor in engine operation. If the oil is too thick, it will resist the efforts of the metal to move relative to the oil, and create drag on the parts. If it is too thin, the metal will force its way through the oil film and create boundary lubrication. The thickness of the oil must therefore be balanced to provide the best compromise between these two extremes.

Webster defines friction as the "rubbing of one body against another," and as "resistance to relative motion between two bodies in contact." Friction can be beneficial. As we overcome this resistance to motion between two objects in contact, heat is generated. This heat is what warms our hands or starts a fire. Friction is also the principle behind the braking systems we find on our automobiles. In fact, once we were able to get a car moving there would be nothing to stop it without friction except the effects of gravity or other objects.

However, friction can also be our enemy. The heat generated as the result of friction can cause damage. Because contact is required to generate friction, wear in the areas of contact can occur. This can lead to material failures, overheating and the formation of wear deposits.

Although there are many ways to reduce friction, the most common way is through the use of a fluid or a semi-fluid material. The key characteristic of such materials is that they are not readily compressible. Fluid and semi-fluid materials allow us to minimize component contact or eliminate contact altogether. These fluids are commonly referred to as lubricants.

Oil that has high VISCOSITY INDEX (VI) is preferable to oil with a low VI.

The viscosity (thickness) of an oil is affected by temperature changes during use. As the oil’s temperature increases, its viscosity will decrease along with its load carrying ability. The degree of change that occurs with temperature is determined by using ASTM test methodology D-2270. Referred to as the oil’s Viscosity Index, the methodology compares the viscosity change that occurs between 100° C (212° F) and 40° C (104° F). The higher the viscosity index, the less the oil’s viscosity changes with changes in temperature. While a greater viscosity index number is desirable, it does not represent that oil’s high temperature viscosity or its load carrying ability. Shearing forces within the engine, and particularly the transmission, can significantly reduce an oil’s viscosity. Therefore, oils with a lower viscosity index but higher shear stability (discussed below) can, in fact, have a higher viscosity at operating temperature than one with a higher viscosity index and lower shear stability.  Thus Oil with High VI does not thin out as much at high temperatures, and does not thicken as much as low temperatures, therefore its flow characteristics are much better over a wide temperature range.

It is important to note that the viscosity of the oil changes as it becomes contaminated. Dirt, oxidation and sludge will increase the viscosity of the oil while fuel dilution will reduce the viscosity.

The Issue with Petroleum Oil

Petroleum Oils range in Viscosity Index from very poor (VI = 0) for Naphthenic California Crude, to relatively good (VI = 100) for Pennsylvania Parafininc Crude.

Typical base stock that is used for lubricants is near the VI 100 range, and to improve it further Viscosity Index Improvers are used. These polymers however are not shear stable and loose their effectiveness in service.

This effect is called the Viscosity break down, and is one reason why frequent oil changes are recommended for Conventional Petroleum Oil.

THE EVOLUTION OF SYNTHETIC OILS

As time goes on, the lubrication needs of equipment continue to change. As equipment becomes more sophisticated, the demands placed upon the required lubricants become more severe. What may have been a preferred lubricant in the past is likely to be totally unacceptable today. The automotive industry is an excellent example of how demands on equipment have changed. The engines used in today’s cars require significantly more from a motor oil than they did only a few years ago. For improved fuel economy, most cars are now using lighter oils. Yet the same cars have engines that put out more power per cubic inch of displacement than ever before. To achieve this power level, designers are adding turbo chargers which expose the oils to higher temperatures and greater stress. Requirements for cleaner exhaust emissions have contributed to higher levels of contaminants in the oil and also increased the oil’s operating temperature. By reducing the aerodynamic drag of new vehicles, designers have also minimized the amount of air that flows over engines and drive trains, and caused operating temperatures to increase still further. Even with all of these changes, designers are still requiring lubricants to last longer than they ever did before. The demand for synthetic lubricants has never been higher.

HOW ARE SYNTHETIC OILS DIFFERENT?

Although the engineering of each synthetic base stock varies depending on the particular stock, synthetics are generally made through a reaction process. This reaction process significantly improves the consistency of the stock and its molecular uniformity. Mineral stocks, on the other hand, are obtained through a process of distillation. Distillation slightly limits the molecular diversity that may exist within the stock, but does not completely eliminate nonessential molecular structures.

This is important because unnecessary molecular structures produce variations in the stock’s performance. The ideal lubricant’s chemical composition is one in which the molecular construction is identical throughout, such as in a synthetic base stock. Because of the way synthetic stocks are produced, they are molecularly uniform and contain significantly less undesirable materials than a mineral base stock. Molecular uniformity also affects the properties that each type of lubricant possesses.

The properties of mineral oils tend to vary due to inconsistencies in the crude from which they are obtained. The properties and performance features of synthetics, on the other hand, are very predictable.

Once again, this is due to their molecular uniformity.

AMSOIL synthetic lubricants are formulated to take advantage of the superior properties of synthetic base stocks. They provide excellent lubrication and wear protection and have been designed to resist the chemical breakdown processes that limit the service life of conventional mineral-based oils.

The Problem With Conventional Petroleum Oil – Protecting Against Rust and Corrosion

Even in a perfectly sealed engine with pure fuel, water will get into the engine and condense on engine parts.

How?

For every gallon of gasoline that is burned, a little over a gallon of water is formed as a by-product. Since the formation of this water vapor is part of normal engine operation, it is part of the oil's job to prevent rust.

The engine is open to another form of corrosion, too.

When the oil becomes contaminated with soot particles from the combustion process (especially problematic in Diesel engines with EGR) and is heated beyond a certain point, it turns from its normal alkaline state to an acidic state. This acid can attack the metal engine parts and cause corrosion unless neutralized quickly.

The Problem with Petroleum Oils

Conventional Petroleum Oils that are not too pure contain sulfur and other chemicals that actually act as rust and corrosion inhibitors.

Highly processed Base Oil like API Group III does however need extra chemical additives to prevent acid formation and corrosion of engine surfaces. In engines that are normally and frequently operated corrosion of the lubricated parts is seldom a problem.

 

To Be Considered a "Good" lubricant, an Oil Must Prevent Wear

Modern day oils are complex, chemically engineered compounds that have improved upon refined crude oil. Modern oils are designed and chemically manufactured to achieve specific traits and properties necessary for use in current automobiles. But many of the basics of lubricants and lubrication are as important today as they were fifty years ago.

To begin with, motor oils must perform some of the same basic functions today as they did years ago. All of these functions are considered when designing any motor oil, whether it will be a synthetic or mineral-based oil.

Once you have started the engine, the oil pump is circulating the oil to the engine parts.

The oil must now prevent the metal-to-metal contact that would result in wear to the moving parts.

Once the engine is running, the oil must prevent metal-to-metal contact by establishing a complete and unbroken film of oil on all critical surfaces. This is what lubrication engineers call full-film lubrication.

Just about any liquid can be called on to provide full-film lubrication under hydrodynamic conditions, such as exist between moving parts (think of tires hydroplaning on a wet street).

However, motor oils must also lubricate and prevent wear. This can be more of a challenge in temperature extremes. Oil that does not flow well in cold temperatures will leave parts of the engine with no protection, and oil that burns off and becomes too fluid will leave little protection in high temperatures. The goal of an oil is to provide constant full-film lubrication to an engine’s components. This type of lubrication occurs when the moving surfaces are continuously separated by a film of oil. Crankshaft bearings as well as connecting rods, cam-shafts and piston rings normally operate with full-film lubrication. Boundary lubrication occurs when it is moving parts and intermittent metal-to-metal contact results. Additives can greatly reduce the amount of damage that can occur during boundary lubrication. Boundary lubrication conditions always exist during engine starting and often during the operation of a new or rebuilt engine.

Synthetic oils have proven themselves to be superior to conventional oils.  This has been proven many times through a test called the 4-ball wear test. 

These test results are usually obtained by an independent testing lab. The 4-ball wear test is a standard ASTM test for determining a lubricants ability to prevent wear. The test is torturous to accelerate wear and produce wear scars between moving ball bearings under load, so a determination of long term wear prevention can be assessed.

In independent tests, AMSOIL Synthetic engine oils produce the smallest wear scars and provides wear protection SUPERIOR to all other oils, whether conventional or synthetic! It actually SLOWS DOWN the wear and aging in your engine and will make it last much longer than normal, not to mention significantly better performance and fuel economy.

Full-film lubrication occurs when the moving surfaces are continuously separated by a film of oil. The viscosity of the oil must remain high enough to prevent metal-to-metal contact. Wear will only occur if the surface is scratched by particles thicker then the oil film as well as substantially harder than the bearing surfaces. Crankshaft bearings, connecting rods, camshaft, and piston pins normally operate with full-film lubrication.

It is what happens when the two pieces of metal stop moving (hydrostatic conditions) that interests us (such as when the piston reaches dead center, and the rings stop relative to the cylinder walls).

Anytime there is metal-to-metal contact, such as during starting when it is almost impossible to maintain full-film lubrication, the situation is termed "boundary lubrication". When this occurs, the friction generated between the surfaces can produce enough heat to temporarily fuse metals together. You might say boundary lubrication is a fact of death in engines.

Another good reason to stop this initial wear is that it then makes subsequent wear less of a problem. For example, even a small amount of primary wear will result in rough spots on the mating surfaces and metal particles in the lubricant. Rough spots wear faster than smooth metal, aided by the dislodged wear particles that are roaming around looking for trouble. This is called secondary wear, because it would not have occurred but for the primary wear.

If you can eliminate the primary wear, and the secondary (and tertiary, etc.) wear problem (improving filtration efficiency) the wear problem ceases to exist.

Over 100 years of real life experience with internal combustion engines the "Conventional" oil companies found that the "ideal" motor oil viscosity is equivalent to SAE 30 oil at normal operating temperatures and normal operating speeds. This oil viscosity prevents metal-to-metal contact by establishing a complete and unbroken film of oil on all critical surfaces at oil temperature ranging from 190°F to 220°F and at typical engine speeds in 2,500 to 4,000 RPM range the full-film lubrication is successfully maintained.

At lower speeds such as those encountered in Heavy Duty Diesels, SAE 40 oil is much better, while in high revving motorcycle or racing engines SAE 20 or even a thinner oil is required.

As engine speed increases the viscosity must be reduced and when engine speed is reduced or load increased the viscosity must be increased. The oil viscosity and engine speed therefore have inverse mathematical relationship.

However, metal to metal contact ALWAYS occurs when petroleum oil is used and therefore various additives must be blended into the lubricant to prevent excessive wear during this boundary operation.

These additives are however also depleted over time and can also chemically "etch" the surface. Although some chemical Additives prevent a mechanical wear, they will actually cause a "chemical" wear.

Conventional Petroleum Oil therefore does not eliminate wear, even with Additives, it only reduces it to an "acceptable" level. 

One other issue that affects wear is making sure that the metal surfaces have an adequate lubricant covering at the time the engine is started.  Everytime you start your engine there is a brief moment before oil pressure is present in the engine. Experts agree that this is when the majority of the mechanical wear occurs.  Dry Starts may occur in as little as a few hours.

Over 80-90% of all engine wear occurs in the first 5-10 seconds when it is first started. Lack of lubrication causes friction, which causes the wear and damage that occurs. This damage is accelerated by the length of time between engine starts.

Pre-lubrication will increase engine life, reduce maintenance, decreased friction allows easier starting from the reduced current draw needed by the starter.

The resulting wear is accumulative... the "Dry Starting" of the engine causes "metal-to-metal" friction at initial startup, however pre-lubrication of the engines with oil eliminates the normal scuffing and friction. "Dry Start" wear is Preventable...

One way to address this problem is the AMS-Oiler™ pre-charger which effectively puts an end to dry-engine starting. Motor oil is injected directly on the engine bearings and other wear-sensitive surfaces upon turning the ignition key. Its rugged construction withstands severe service and platforms reliably in any personal, commercial or industrial application. Outperforms gas and air-charge systems. Mechanical life cycle exceeds one million engine starts, with no maintenance required.

What Effect Does Base Stock Have to Oil Performance?

When we talk about "base stock" we are referring to the base fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants.

Most motorists are most familiar with mineral oil base stock lubricants, as they account for close to 94 percent of the motor oil sold in USA today. This was not always the case, however, and the day may come when mineral oils again take the back seat.

• "Traditional" base stocks

In spite of its dominance of modern lubrication, mineral oil was not always the lubricant of choice. Olive oil was used to lubricate wooden planks some 3500 years ago for moving heavy loads. Throughout history, oils made from rapeseed, castor beans, palms, lard, wool grease, and sperm whales have been used. Some of these materials are still in use today, combined with modern additives.

One motor oil, for example, combines a mineral oil base with a percentage of oil from the jojoba plant, along with an additive package. Another manufacturer makes a lubricant for racing cycles with a pure castor bean base. These so-called natural oils are different from mineral oils in that they have oxygen atoms in the molecule in addition to the hydrogen and carbon atoms.

• Mineral oil base stocks

Mineral oil base stocks are refined from crude oil, the stuff they pump out of the ground. By varying the temperature and pressure at which the crude oil is processed, refiners can "crack" the crude oil to obtain asphalt or jet fuel, and everything in between.

Crude oils fall into two categories, Paraffinic (as in wax) and Naphthenic. Within each of these two categories are two sub-categories, neutral stock and bright stock. Paraffinic oils have a naturally high viscosity index (see below for an explanation of viscosity index), but are converted into varnish and hard deposits under heat. Naphthenic oils are naturally clean and are clean burning, but have poor viscosity indexes.

Whichever type of crude they start with, after cracking the refiners are left with lighter and heavier weights of base oil. Neutral stock is the thinner component of oil, while bright stock is the thicker component. When compounding petroleum oils, engineers are confronted with balancing the pros and cons of these four diverse elements in order to come up with a usable base stock.

The Conventional Petroleum base stocks that are used for lubricating oil production are further classified by API based on the base oil properties into several "groups"

          API Group I, API Group II and API Group III

• The Base oil producers then further distinguish between the lower cost and higher cost base oil products by labeling them as API Group II plus, or marketing API Group III as "synthetic".
• Petroleum-based lubricants contain very large molecules, and especially suffer from thermal degradation when exposed to high engine temperatures. When this happens, they also form varnish deposits, which stick rings to the pistons and plug up turbo oil passages. Once a petroleum based oil reaches 475°F, it breaks down, turns into tar and varnish and then forms hard deposits that block the oil flow.

            Synthetic base stocks

• Animal, vegetable, and mineral oils are either extracted or refined. But there is another way to obtain a lubricant, and that is to build it from scratch. This is how the synthetics are made.
• Historically, synthetics have been around in one form or another for close to 60 years, starting with research into new hydrocarbon liquids in the laboratories of Standard Oil of Indiana in the early 1930s. During WWII, German and Italian scientists developed synthetic lubricants that would allow their machinery to operate in the intense cold of the Russian front. In the late 1940s, British and American scientists realized that the new jet engines would need a special lubricant if they were to fly at all, and synthetics were developed for that application.
• But all synthetic base stocks are not alike, either in construction or in behavior. Out of the 18 or more synthetic base stocks, only four are currently of interest to us as internal combustion engine lubricants. Dibasic acid esters (diesters) and monobasic acid esters of polyol (polyol esters) are both of the ester family. Alkylated aromatics (dialkylbenzenes) and olefin oligomers (Polyalphaolefin, or PAO) are of the synthesized hydrocarbon family.

API classifies PAO as API Group IV base stock, and all other "non-conventional oil" no matter if they are synthetic or not as API Group V base stock.

Some companies, notably SHELL and CASTROL market API Group III Petroleum based oil as "synthetic".