lazerator
Aerospace
- May 18, 2003
- 3
I'm attaching a paper I've written as an introduction to oil for automotive enthusiasts. Much of the information has been gleamed from this forum and I'd like to thank those who contributed. The references in the paper are a bit lacking and I would appreciate being pointed in the right direction regarding papers and publications that I can use to verify or refute statements made I've written in the article before it sees daylight.
----Begin Article-----
Oil Basics
Author: Samuel Lazerson
Date: August 15, 2003
It has been called the lifeblood of our engines. It is used to lubricate, cool and monitor the condition of an engine. It actuates modern valvetrain parts in many modern engines. Oil ,still misunderstood by the automotive enthusiast community, is as important to our engines as fuel. Arguments often arise over what oil to use in which engine. The debate in the synthetic vs. natural oil still rages on. Furthermore, arrays of additives have flooded the market. While each promises greater gas economy and smoother engine operation, little is published regarding their chemical makeup. What may be even more disturbing is the use of oil without consideration of driving conditions. This article will clarify some of the confusion and misunderstandings.
All oils will have an American Petroleum Institute (API) Service rating, viscosity grade and energy-conserving indicator. The API service rating indicates the engine requirement. The viscosity rating of the oil indicates the ability of the oil to flow in centistroke (cSt). This is then converted to an American Society of Engineers (ASE) weight number. With the advent of multi weight oils by the addition of polymers, a two number system is designated. The first number refers to the low temperature viscosity while the second number refers to the oil viscosity at 100°C. At low temperatures the polymer chains are coiled and unravel as they increase in temperature. This helps to maintain fairly narrow viscosity ranges. The ability to choose the correct oil requires one to know exactly the meaning of these values.
The API service rating is given to oils to ensure the quality of the oil.
"To assure consumers of high quality lubricating oils for their vehicles. Motor oil that carries the API Service Symbol, or "donut," and API Certification Mark, or "starburst," has been tested to ensure that it protects against rust and corrosion, wear, oil thickening and deposits and sludge. The "donut" also identifies the performance category for oil, distinguishing products for gasoline engines and diesel engines of various types." (
As of this writing it is recommended to use an SL rated oil in unleaded engines. As standards for emission and engine performance change, new ratings are created. The current API Motor Oil Guide can be found at the API website. ( It is important to verify that the API Certification Mark on an oil is genuine, as there have been incidents of companies falsifying the mark.
"BI-LO, LLC, a grocery store chain operating in North Carolina, South Carolina, Georgia, and Tennessee, is removing from sale all bottles of Star brite 10W-30, 10W-40 and 20W-50 Motor Oil displaying the API Certification Mark® "Starburst" and API Service Symbol® "Donut." These oils are not licensed by API to display the API marks and do not meet the performance level deemed necessary for most vehicles in use today. Consumers should not use these oils in their vehicles and should return unused portions to BI-LO." (
While most major manufacturers do not intentionally falsify this information, it is important to realize that a lesser-known brand may not meet industry standards. The API service rating is an important mark that allows a buyer to know that the product meets industry standards and indicates proper oil usage.
The viscosity of an oil is its ability to flow. In referring to a fluid's viscosity, centistroke, is a commonly used measurement which is a misnomer. The true viscosity of fluid is its resistance to the relative motion of its components. Often measured in poise and centipoise. Poise is normalized to the viscosity of water. When this value is divided by the specific gravity of the fluid in question the resulting value is considered the Kinematic Viscosity, calculated in centistroke. This value can then be converted to a Society of Automotive Engineers (SAE) weight designation. The SAE has the following weight designations 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50 and 60. The "W" refers to low-temperature (40°C) performance while numbers lacking this designation are designed for high temperature operation (100°C). The oils used currently in most motor vehicles are multi-grade oils. They offer both high and low temperature viscosity designations. These oils have allowed modern engines to operate with one type of oil throughout the year. Understanding viscosity allows one to choose an oil for a given situation.
Many companies make claims regarding their oil additives. These additives are simply mixtures of trace elements and an oil suspension (the same trace elements that are added to oil by the manufacturers to set their product apart). The elements range from argon to silicon and are usually a part of more complex molecules. Each chemical is added to improve different properties of the oil. Most additives are designed to increase anti-wear and extreme pressure properties, the latter more so in the case of gear oils. The additive packages sold, increase the concentrations of these chemicals in the oil, resulting in increased levels of sulfur and potassium. Current EPA trends are to decrease these elements, inspite of the fact these chemicals improve the properties of the oil. Additives seek to reverse this trend and improve the properties of the oil.
Today most oils have a concentration of .25%-1% zinc dialkly-dithiophosphates (ZDDP). This chemical is used to improve anti-wear and extreme pressure properties of the oil. It achieves this by reacting with the metal under extreme pressure (contact area between bushings and gears) to form a protective film. During combustion this chemical releases SOx and POx into the exhaust stream and crankcase oil. Being highly reactive with organic substances it can begin to degrade the oil. SOx and POx will compete with NOx emissions in the catalytic converter, lowering its effectiveness. In contrast to lead, they do not permanently damage the converter. As a result the long-term effects can be negated if the converter is allowed to regenerate. Above 1% it has been thought that the ZDDP will begin to settle out of the oil. ZDDP is marketed under many names by chemical manufactures. It is important to note that these additives are used to manufacture oils that meet specialized standards and should not be considered a replacement for regular oil changes.
The factors that necessitate oil changes depend primarily on operating conditions. Outside air enters and mixes with the oil contained in the crankcase. Particles in the 5-15 micron range do the most damage to engine parts, as they do not settle out, unlike larger particles. These smaller particles are of the same size range as the protective films formed by the additives in the oil. As oil burns it becomes oxidized by, SOx, NOx and POx entering the crankcase. Detergents are added to slow this process and once the detergent levels fall low enough, the oil quickly degrades. Soot (10-100nm), dispersed in the oil, produces a viscosity increase in oil in addition to turning the oil black. Concentrations of soot have reached 1.5% by the time oil is removed. Engines that are burning oil need to have their oil changed more often because of the accelerated introduction of SOx, NOx and POx into the oil. Engines that are not run often should also have their oil changed at the manufacturers recommended interval, usually every 6 months. Oils will degrade with time even if not run though an engine. Oil change intervals are best determined by closely monitoring the physical properties of the oil, eg. color and texture.
Oil is one of the most important fluids in a car. It lubricates and cools the moving parts of the engine. Understanding the types of oil, their uses and their properties is essential to choosing an oil for the engine. Additives are essential to the development of modern oil formulas. Without a thorough understanding of the composition of the oil, it is unwise to alter the component concentrations. The oil change cycle for an engine is a function of driving conditions and should be changed as scheduled by the manufacture. It is important to monitor oil properties to gauge the necessity of a decrease in the oil change interval. Hopefully this has given one some insight into oil, its components and what to think about when changing oil.
-----End Article----
----Begin Article-----
Oil Basics
Author: Samuel Lazerson
Date: August 15, 2003
It has been called the lifeblood of our engines. It is used to lubricate, cool and monitor the condition of an engine. It actuates modern valvetrain parts in many modern engines. Oil ,still misunderstood by the automotive enthusiast community, is as important to our engines as fuel. Arguments often arise over what oil to use in which engine. The debate in the synthetic vs. natural oil still rages on. Furthermore, arrays of additives have flooded the market. While each promises greater gas economy and smoother engine operation, little is published regarding their chemical makeup. What may be even more disturbing is the use of oil without consideration of driving conditions. This article will clarify some of the confusion and misunderstandings.
All oils will have an American Petroleum Institute (API) Service rating, viscosity grade and energy-conserving indicator. The API service rating indicates the engine requirement. The viscosity rating of the oil indicates the ability of the oil to flow in centistroke (cSt). This is then converted to an American Society of Engineers (ASE) weight number. With the advent of multi weight oils by the addition of polymers, a two number system is designated. The first number refers to the low temperature viscosity while the second number refers to the oil viscosity at 100°C. At low temperatures the polymer chains are coiled and unravel as they increase in temperature. This helps to maintain fairly narrow viscosity ranges. The ability to choose the correct oil requires one to know exactly the meaning of these values.
The API service rating is given to oils to ensure the quality of the oil.
"To assure consumers of high quality lubricating oils for their vehicles. Motor oil that carries the API Service Symbol, or "donut," and API Certification Mark, or "starburst," has been tested to ensure that it protects against rust and corrosion, wear, oil thickening and deposits and sludge. The "donut" also identifies the performance category for oil, distinguishing products for gasoline engines and diesel engines of various types." (
As of this writing it is recommended to use an SL rated oil in unleaded engines. As standards for emission and engine performance change, new ratings are created. The current API Motor Oil Guide can be found at the API website. ( It is important to verify that the API Certification Mark on an oil is genuine, as there have been incidents of companies falsifying the mark.
"BI-LO, LLC, a grocery store chain operating in North Carolina, South Carolina, Georgia, and Tennessee, is removing from sale all bottles of Star brite 10W-30, 10W-40 and 20W-50 Motor Oil displaying the API Certification Mark® "Starburst" and API Service Symbol® "Donut." These oils are not licensed by API to display the API marks and do not meet the performance level deemed necessary for most vehicles in use today. Consumers should not use these oils in their vehicles and should return unused portions to BI-LO." (
While most major manufacturers do not intentionally falsify this information, it is important to realize that a lesser-known brand may not meet industry standards. The API service rating is an important mark that allows a buyer to know that the product meets industry standards and indicates proper oil usage.
The viscosity of an oil is its ability to flow. In referring to a fluid's viscosity, centistroke, is a commonly used measurement which is a misnomer. The true viscosity of fluid is its resistance to the relative motion of its components. Often measured in poise and centipoise. Poise is normalized to the viscosity of water. When this value is divided by the specific gravity of the fluid in question the resulting value is considered the Kinematic Viscosity, calculated in centistroke. This value can then be converted to a Society of Automotive Engineers (SAE) weight designation. The SAE has the following weight designations 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50 and 60. The "W" refers to low-temperature (40°C) performance while numbers lacking this designation are designed for high temperature operation (100°C). The oils used currently in most motor vehicles are multi-grade oils. They offer both high and low temperature viscosity designations. These oils have allowed modern engines to operate with one type of oil throughout the year. Understanding viscosity allows one to choose an oil for a given situation.
Many companies make claims regarding their oil additives. These additives are simply mixtures of trace elements and an oil suspension (the same trace elements that are added to oil by the manufacturers to set their product apart). The elements range from argon to silicon and are usually a part of more complex molecules. Each chemical is added to improve different properties of the oil. Most additives are designed to increase anti-wear and extreme pressure properties, the latter more so in the case of gear oils. The additive packages sold, increase the concentrations of these chemicals in the oil, resulting in increased levels of sulfur and potassium. Current EPA trends are to decrease these elements, inspite of the fact these chemicals improve the properties of the oil. Additives seek to reverse this trend and improve the properties of the oil.
Today most oils have a concentration of .25%-1% zinc dialkly-dithiophosphates (ZDDP). This chemical is used to improve anti-wear and extreme pressure properties of the oil. It achieves this by reacting with the metal under extreme pressure (contact area between bushings and gears) to form a protective film. During combustion this chemical releases SOx and POx into the exhaust stream and crankcase oil. Being highly reactive with organic substances it can begin to degrade the oil. SOx and POx will compete with NOx emissions in the catalytic converter, lowering its effectiveness. In contrast to lead, they do not permanently damage the converter. As a result the long-term effects can be negated if the converter is allowed to regenerate. Above 1% it has been thought that the ZDDP will begin to settle out of the oil. ZDDP is marketed under many names by chemical manufactures. It is important to note that these additives are used to manufacture oils that meet specialized standards and should not be considered a replacement for regular oil changes.
The factors that necessitate oil changes depend primarily on operating conditions. Outside air enters and mixes with the oil contained in the crankcase. Particles in the 5-15 micron range do the most damage to engine parts, as they do not settle out, unlike larger particles. These smaller particles are of the same size range as the protective films formed by the additives in the oil. As oil burns it becomes oxidized by, SOx, NOx and POx entering the crankcase. Detergents are added to slow this process and once the detergent levels fall low enough, the oil quickly degrades. Soot (10-100nm), dispersed in the oil, produces a viscosity increase in oil in addition to turning the oil black. Concentrations of soot have reached 1.5% by the time oil is removed. Engines that are burning oil need to have their oil changed more often because of the accelerated introduction of SOx, NOx and POx into the oil. Engines that are not run often should also have their oil changed at the manufacturers recommended interval, usually every 6 months. Oils will degrade with time even if not run though an engine. Oil change intervals are best determined by closely monitoring the physical properties of the oil, eg. color and texture.
Oil is one of the most important fluids in a car. It lubricates and cools the moving parts of the engine. Understanding the types of oil, their uses and their properties is essential to choosing an oil for the engine. Additives are essential to the development of modern oil formulas. Without a thorough understanding of the composition of the oil, it is unwise to alter the component concentrations. The oil change cycle for an engine is a function of driving conditions and should be changed as scheduled by the manufacture. It is important to monitor oil properties to gauge the necessity of a decrease in the oil change interval. Hopefully this has given one some insight into oil, its components and what to think about when changing oil.
-----End Article----
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