Motor Oil

[MountaineerTom]

From the Valvoline website.  Just some info on oil that I've seen questions about.

 

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Oil Viscosity

Weighing in on engine lubrication

 

by:

Wayne Scraba

 

 

Most people are familiar with oil's Viscosity Rating—SAE 10W-40, for example. However, very few know that the "W" refers to "winter," not "weight." And most of us have no idea what the weight-rating numbers mean other than that the vehicle's manufacturer specifies a particular viscosity. This story deals strictly with viscosity; we're saving the petroleum vs. synthetic debate for later.

 

Oil Duties

 

Inside an engine, oil is in a Catch-22 scenario: It has to seal rings and valves, but it also must reduce friction. In simple terms, oil has to accomplish two functions that have directly opposite requirements.

 

 

The viscosity of any oil changes with temperature. The higher the temperature, the lower the viscosity—the oil thins out. On the flipside, the lower the temperature the higher the viscosity. Because of this, the Society of Automotive Engineers (SAE) has established a series of classifications that establish oil viscosity at 100 and 0 degrees Celsius (212 and 32 degrees Fahrenheit, respectively).

 

Highs and Lows

 

Low-viscosity oils flow better than high-viscosity ones—the lighter-weight fluid is easier to pump and therefore circulates faster through the engine's various galleries. Low-viscosity oils also maintain a lower oil pressure, but the oil pump delivers a greater volume through the galleries than it would with thicker (higher-viscosity) oils. Heavier oils also tend to operate at higher temperatures because the oil pump has to work harder to force the lubricant through the system. Oil does not compress readily, so the added pressure increases the temperature. In the end, high-viscosity oils maintain a higher oil pressure, but the pump delivers a smaller volume of oil.

 

Multigrades

 

Multigrade oils typically begin as base oils, such as 10W. Then viscosity-index modifiers (polymers) are added in an effort to stabilize the viscosity. This allows a SAE 10W-40 oil to flow like a 10W at cold temperatures and a 40W at higher temperatures.

 

 

The multigrade oils' viscosity modifiers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss. Permanent viscosity loss occurred when high shear forces (such as the relationship between the main bearings and the crankshaft) actually break the polymer molecules into less-effective smaller pieces. On a similar note, temporary viscosity loss also occurred when the polymer molecules aligned themselves in order to create a path of least resistance.

 

 

Fortunately, today's additive packages have improved oil's shear-resistance. However, oils with the same rating from different manufacturers can exhibit different viscosity ratings in an operating engine, depending on the shear stability of their viscosity-modifying additives.

 

 

For technoids, weights are defined thusly (stokes and centistrokes are measurements of viscosity):

 

 

"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt.

 

 

"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt.

 

 

"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt.

 

 

"SAE 60 is SAE 60 no matter what the "W" prefix number is: 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 21.9 cSt and a maximum of 26.1 cSt.

 

 

"There is no SAE 70 and no one is likely to make one with a "W" prefix number although it is possible using a synthetic base oil. This viscosity is identified as Grade 70. The viscosity @ 100 degrees C has a minimum of 26.1 cSt and no maximum."

 

 

The difference between a multigrade and a singlegrade oil: The singlegrade can't pass the low temperature viscosity test. If it did meet one of the following "W" viscosities, it would be a multigrade.

 

 

Singlegrade oils will become obsolete for performance engines in the future. We dropped SAE 30 and SAE 40 because SAE 10W-40 does everything 30 or 40 can do—and some things the straight grades can't do—like increasing horsepower. If an off-roader doesn't like SAE 10W-40, then use 20W50. It can do everything a SAE 10W-40 can do except pass the sub-zero viscosity test at -20 degrees C.

 

 

Multigrade viscosities are run at six different sub-zero temperatures. When a racing-oil designer puts a formula together, he has to know the viscosity at 100 degrees C of every component in the additive composition. He has to have a target viscosity objective for the finished oil in each SAE grade. Once a formula is established, the technician who supervises the blending has to duplicate this formula in the correct proportions every time the product is blended. The viscosity at 100 degrees C has a plus or minus written into the oil's quality-control specification.

 

Multigrade or Multi-Vis?

 

One oil manufacturer claims that "some people in the industry use multi-viscosity as if it means the same thing as multigrade. An oil cannot be multi-viscosity, but it can be multigrade by meeting the viscosity requirements for SAE 30, 40, 50 or 60 and one of the sub-zero "W" viscosity requirements. At one time, some oil companies labeled oils SAE 10W, 20W30—as if the oil could be 10W and 20W at the same time. This is impossible because 10W is measured at -25 degrees C and 20W is measured at -15 degrees C, which eliminates the multi-viscosity theory."

 

API Numbers

 

Shortly after WWII, the American Petroleum Institute (API) developed a system that established three basic types of engine oils: regular, premium and heavy-duty. Naturally, three oil classifications could never hope to cover all of the different applications ranging from conventional passenger cars to heavy-duty trucks. The API eventually realized that other variables had to be considered, such as the type of engine and its usage. In 1952, the API launched the service classifications system.

 

 

The API system revolves around two general classification: S for Service (typical passenger cars and light trucks) and C for commercial applications (typical diesel equipment). The breakdown of "S" varieties is as follows:

 

 

SA: This is a plain mineral oil that doesn't contain additives common in today's high-tech lubricants. This oil was primarily used in the 1920s and is obsolete today.

 

 

SB: Lubes that contain anti-wear and oxidation inhibitors as well as corrosion inhibitors. This oil was primarily in use prior to 1964 and was created for vehicles that saw moderate conditions. API SB oils are still recommended today by some compressor manufacturers, but should never be used in modern gasoline engines.

 

 

SC: This classification was originally recommended for use in 1964-67 vehicles. It contains additives that control rust, wear, corrosion and engine deposits. It too is now obsolete.

 

 

SD: SD lubes were recommended for use in 1968-70 vehicles as well as certain post-1970 passenger cars. This oil contains the same additive packages as the SC class and can be used in place of it. It too is now obsolete.

 

 

SE: This category was recommended for certain 1971 vehicles as well as most 1972 - 1979 vehicles. This classification offers more protection than the SD group of lubricants and is suitable for severe-duty applications. This classification can be used in place of SD oils. It too is now obsolete.

 

 

 

 

SF: Recommended for 1980 - 1989 passenger vehicles. This oil has superior anti-wear properties and enhanced oxidation stability over SE lubricants. It too is now obsolete.

 

 

SG: The SG rating was introduced in 1989 and combined the performance properties of the commercial rating CC (lubricants designed for use in supercharged/turbocharged diesel applications in moderate to severe service). It too is now obsolete.

 

 

SH: Now obsolete, SH was designed for 1996 and older engines.

 

 

SJ: Introduced in 1996, this rating is for all automotive engines presently in use.

 

 

SL: Introduced in 2001, SL provides improved overall performance for 2002 model year vehicles, including oxidation resistance, deposit control, fuel economy, and low temperature properties.

 

 

Generally speaking, think of the API system as a blueprint for oil. In order to gain an API classification, oil manufacturers have to follow a set of limitations. This creates a few problems for oil companies, especially those who produce racing oils. Racing oil must conform to viscosity-grade standards but not necessarily to those for chemical-additive composition or base-oil composition. That's why you'll find several brands of racing oil without API classifications.

 

Racing Oil

 

In the old days, high-performance "racing" oils were generally sold in a straight 50 grade. Today, you have much more choice. There are dozens upon dozens of oils to choose from (even from one manufacturer or "packager"). The following five questions should influence your selection of oil viscosity:

 

 

(1) Does the engine operate on racing gasoline, alcohol or nitromethane? (2) Is the powerplant normally aspirated, turbocharged or supercharged? (3) Is there an oxidizer such as nitrous oxide or propylene oxide present? (4) How long will the engine be running and if racing, what is the duration of the race? (5) How often is the oil changed?

 

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The Science Behind Synthetics

 

 

SynPower uses the power of advanced synthetic technology to improve performance. Find out what makes synthetics work in Inside Synthetic Technology and learn how synthetics outperform conventional products in The Big Difference.

 

Inside Synthetic Technology

 

The power behind synthetics lies in the basic building blocks that make up every SynPower product. Synthetics are created with molecules specially made, or synthesized, for improved performance.

 

 

In contrast, conventional products use naturally occurring substances such as mineral oil. The molecules found in such substances are very diverse and some may have "weak links." Therefore, they are more likely to break down under the extreme conditions modern engines can dish out. But SynPower motor oil molecules are specifically designed to be more consistent in structure and more stable. The weak links have been eliminated. So you can expect SynPower synthetic motor oil to resist breakdown and perform significantly better than conventional motor oils - even under extreme conditions.

 

The Big Difference

 

Conventional products, such as motor oils, are based on mineral oil, which comes from crude oil. Crude oil is formed over thousands of years from decomposing trees and other organic materials under extreme pressure and heat deep within the earth.

 

 

Crude oil contains hundreds of thousands of different types of molecules that come in various shapes and sizes. The lubricating qualities of these molecules can range from very good, to okay, to not so good, to downright awful. Through the refining process, the most "unsuitable" ingredients are removed to produce the mineral oils.

 

 

The refined mineral oils still contain a variety of different molecules that have different sizes, shapes and lubricating qualities. Therefore, they will perform at different levels, break down at different rates, and be affected differently by heat, pressure and other factors inside your engine.

 

 

In contrast, synthetics use molecules made (or synthesized) to fit a specific molecular design. Through a variety of chemical processes, molecules in synthetic products can be consistently made with the right shapes or sizes, or to provide specific performance characteristics or to enhance lubricating quality. In fact, the molecules used in SynPower products are made to provide the ultimate in consistency and performance.

 

 

Because its synthetic molecules are "made to order," your SynPower Brake Fluid can have a higher wet boiling point than ordinary DOT 3 brake fluids - reducing the chance of vapor forming in your brake system. SynPower Fuel System Treatments can have just the right mix of molecules to better target and remove specific types of build-ups, such as hard carbon deposits on top of intake valves. And SynPower engine oil can withstand extremes better than even the best conventional motor oils, giving you the ultimate protection.

 

The Additive Touch

 

The base fluids used only tell part of the story for SynPower products. The other key elements are the performance chemicals that Valvoline chemists add to the fluid. These include dispersants, detergents, anti-foaming agents, anti-oxidants, friction modifiers, anti-wear agents and others.

 

 

Products such as SynPower Power Steering Fluid utilize some of these special conditioners and additives to help stop problems such as squealing and leakage and to protect against pump breakdown caused by wear, oxidation and foaming.

 

 

Valvoline chemists call on the over 135 years of Valvoline Motor Oil experience and over 100 years of Valvoline Racing experience to select only the best components and combine them in just the right proportions. Put these in our superior synthetic base fluids and you have the best lubricants science can provide.

 

Powerful Performance

 

SynPower has a complete line of synthetic products to help your car achieve and maintain maximum performance. Each SynPower product is custom-designed for a specific application.

 

 

Every system and part under your hood operates under unique conditions. Varying levels of heat, pressure, exposure to contaminants and other factors create different challenges for cleaners, fluids and lubricants. Therefore, each SynPower product is designed with custom-made molecules and additives to meet these specific demands.

 

 

For example, SynPower Fuel System Treatment contains special synthetic cleaners that attack deposits without damaging vital seals and gaskets. These cleaners specifically target the kind of deposits found on fuel injectors, intake valves, combustion chambers and manifolds to restore maximum power and performance while eliminating rough idle, hesitation and knocking.

 

 

Active ingredients in other SynPower products are similarly engineered to provide unique benefits to maximize your car's performance.