An oil is a substance that is in a viscous liquid state ("oily") at ambient temperatures or slightly warmer, and is both hydrophobic, (immiscible with water, literally "water fearing") and lipophilic (miscible with other oils, literally "fat loving").


All oils, with their high carbon and hydrogen content, can be traced back to organic sources or space. Mineral oils, found in porous rocks underground, are no exception, as they were originally the organic material, such as dead plankton, accumulated on the seafloor in geologically ancient times. Through various geochemical processes this material was converted to mineral oil, or petroleum, and its components, such as kerosene, paraffin waxes, gasoline, diesel and such. These are classified as mineral oils as they do not have an organic origin on human timescales, and are instead derived from underground geologic locations, ranging from rocks, to underground traps, to sands.
PETROLEUM is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds.
COMPOSITION The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium.

  • Carbon   -  83-87%
  • Hydrogen   -  10-14%
  • Nitrogen   -  0.1-2%
  • Oxygen   -  0.1-1.5%
  • Sulfur   -  0.5-6%
  • Metals   -   ≤1000 ppm

Petroleum is found in porous rock formations in the upper strata of some areas of the Earth's crust. There is also petroleum in oil sands (tar sands). Known reserves of petroleum are typically estimated at around 140 cubic km (1.2 trillion (short scale) barrels without oil sands, or 440 cubic km (3.74 trillion barrels) with oil sands. Consumption is currently around 84 million barrels (13.4*106 m3) per day, or 3.6 cubic km per year. Because the energy return over energy invested (EROEI) ratio of oil is constantly falling as petroleum recovery gets more difficult, recoverable oil reserves are significantly less than total oil-in-place. At current consumption levels, and assuming that oil will be consumed only from reservoirs, known recoverable reserves would be gone around 2039, potentially leading to a global energy crisis. However, there are factors which may extend or reduce this estimate, including the rapidly increasing demand for petroleum in China, India, and other developing nations; new discoveries; energy conservation and use of alternative energy sources; and new economically viable exploitation of non-conventional oil sources.


Octane, a hydrocarbon found in petroleum, lines are single bonds, black spheres are carbon, white spheres are hydrogen.


Scope: The petroleum industry generally classifies crude oil by the geographic location it is produced in (e.g. West Texas, Brent, or Oman, its API gravity (an oil industry measure of density), and by its sulfur content. Crude oil may be considered light if it has low density or heavy if it has high density; and it may be referred to as sweet if it contains relatively little sulfur or sour if it contains substantial amounts of sulfur.
The geographic location is important because it affects transportation costs to the refinery. Light crude oil is more desirable than heavy oil since it produces a higher yield of gasoline, while sweet oil commands a higher price than sour oil because it has fewer environmental problems and requires less refining to meet sulfur standards imposed on fuels in consuming countries. Each crude oil has unique molecular characteristics which are understood by the use of crude oil assay analysis in petroleum laboratories.


The petroleum industry is involved in the global processes of exploration, extraction refining, transporting (often with oil tankers and pipelines, and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline (petrol). Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics. The industry is usually divided into three major components: upstream, midstream and downstream. Midstream operations are usually included in the downstream category.


The most common method of obtaining petroleum is extracting it from oil wells found in oil fields. With improved technologies and higher demand for hydrocarbons various methods are applied in petroleum exploration and development to optimize the recovery of oil and gas (Enhanced Oil Recovery, EOR). Primary recovery methods are used to extract oil that is brought to the surface by underground pressure, and can generally recover about 20% of the oil present. The natural pressure can come from several different sources; where it is provided by an underlying water layer it is called a water drive reservoir and where it is from the gas cap above it is called gas drive. After the reservoir pressure has depleted to the point that the oil is no longer brought to the surface, secondary recovery methods draw another 5 to 10% of the oil in the well to the surface. In a water drive oil field, water can be injected into the water layer below the oil, and in a gas drive field it can be injected into the gas cap above to repressurize the reservoir. Finally, when secondary oil recovery methods are no longer viable, tertiary recovery methods reduce the viscosity of the oil in order to bring more to the surface. These may involve the injection of heat, vapor, surfactants, solvents, or miscible gases as in carbon dioxide flooding.
During the oil price increases since 2003, alternatives methods of producing oil gained importance. The most widely known alternatives involve extracting oil from sources such as oil shale or tar sands. These resources exist in large quantities; however, extracting the oil at low cost without excessively harming the environment remains a challenge.
It is also possible to chemically transform methane or coal into the various hydrocarbons found in oil. The best-known such method is the Fischer-Tropsch process.


Diesel or diesel fuel in general is any fuel used in diesel engines. The most common is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted.


Diesel engines are a type of internal combustion engine. Rudolf Diesel originally designed the diesel engine to use vegetable oils as a fuel in order to help support agrarian society and to enable independent craftsmen and artisans to compete with large industry..


Diesel refining Petroleum diesel, or petrodiesel, is produced from petroleum and is a hydrocarbon mixture, obtained in the fractional distillation of crude oil between 200°C and 350°C at atmospheric pressure.


Petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n, iso, and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). The average chemical formula for common diesel fuel is C12H23, ranging from approx. C10H20 to C15H28.


Unlike Petroleum ether and Liquefied petroleum gas engines, diesel engines do not need electrical ignition when burned. Ignition of diesel only occurs under high pressure or with very high temperature. A car running on diesel compresses the diesel inside the cylinder to immense pressure, which causes ignition at normal operating temperatures (glow plugs are used to pre-warm cylinders too reach a minimum temperature). This has some important advantages as simpler possible engine designs which result in more durable engines. This the main reason for this kind of fuel to be in military use in armoured fighting vehicle like tanks, humvees etc. Engines running on diesel also are less likely to stall; as they run at a low RPM, they will rather stutter a lot before stalling.
A big disadvantage of diesel as a vehicle fuel is that it doesn't run well at lower temperatures so, for it to start the cylinder needs to be preheated before starting the engine. Modern diesel engines use advanced motor management mostly nullifying the practical problem as it only takes a little longer to start the engine compared to engines running on an other kind of fuel.


Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce less greenhouse gas pollution. Their greater economy is due to the higher energy per-litre content of diesel fuel and the intrinsic efficiency of the diesel engine. While petrodiesel's 15% higher density results in 15% higher greenhouse gas emissions per litre compared to gasoline,the 20-40% better fuel economy achieved by modern diesel-engine automobiles offsets the higher-per-liter emissions of greenhouse gases, and produces 10-20 percent less GHG emissions than comparable gasoline vehicles. However, the EPA carbon footprint estimates do not include the carbon cost of vehicle manufacture, nor the carbon cost of filtering particulates, sulfates, and nitrates emissions. Biodiesel-powered diesel engines offer substantially improved emission reductions compared to petro-diesel or gasoline-powered engines, while retaining most of the fuel economy advantages over conventional gasoline-powered automobiles.


Wood, hemp, straw, corn, garbage, food scraps, and sewage-sludge may be dried and gasified to synthesis gas. After purification the Fischer-Tropsch process is used to produce synthetic diesel. This means that synthetic diesel oil may be one route to biomass based diesel oil. Such processes are often called Biomass-To-Liquids or BTL.
Synthetic diesel may also be produced out of natural gas in the Gas-to-liquid(GTL) process or out of coal in the Coal-to-liquid (CTL) process. Such synthetic diesel has 30% less particulate emissions than conventional diesel.


Biodiesel refers to a non-petroleum-based diesel fuel consisting of short chain alkyl (methyl or ethyl) esters, made by transesterification of vegetable oil, which can be used (alone, or blended with conventional petrodiesel) in unmodified diesel-engine vehicles.
Biodiesel can be obtained from vegetable oil (vegidiesel/vegifuel), or animal fats (bio-lipids, using transesterification. Biodiesel is a non-fossil fuel alternative to petrodiesel. It can also be mixed with petrodiesel in any amount in modern engines, though when first using it, the solvent properties of the fuel tend to dissolve accumulated deposits and can clog fuel filters. Biodiesel has a higher gel point than petrodiesel, but is comparable to diesel.


Oils are also produced by plants, animals and other organisms through organic processes, and these oils are remarkable in their diversity. Oil is a somewhat vague term to use chemically, and the scientific term for oils, fats, waxes, cholesterol and other oily substances found in living things and their secretions, is lipids.
Lipids, ranging from waxes to steroids, are somewhat hard to characterize, and are united in a group almost solely based on the fact that they all repel, or refuse to dissolve, in water, and are however comfortably miscible in other liquid lipids. They also have a high carbon and hydrogen content, and are considerably lacking in oxygen compared to other organic compounds and minerals.


Almost all oils burn in air generating heat, which can be used directly, or converted into other forms of energy by various means, for example, heating water into steam which is funneled into a turbine which turns a huge magnet. This spins and generates electricity. Oils are used as fuels for heating, lighting (e.g. kerosene lamp), powering combustion engines, and other purposes. Oils used for this purpose nowadays are usually derived from petroleum, (fuel oil, diesel oil, petrol (gasoline), etc), though biological oils such as biodiesel are gaining market share.


Many oils have higher boiling points than water and are electrical insulators, making them useful for liquid cooling systems, especially where electricity is used.


Due to their non-polarity, oils do not easily adhere to other substances. This makes oils useful as lubricants for various engineering purposes. Mineral oils are more suitable than biological oils, which degrade rapidly in most environmental conditions.


Color pigments can be easily suspended in oil, making it suitable as supporting medium for paints. The slow drying process and miscibility of oil facilitates a realistic style. This method has been used since the 15th century.


WEIGHTS The weights given on oils are arbitrary numbers assigned by the S.A.E. (Society of Automotive Engineers). These numbers correspond to "real" viscosity, as measured by several accepted techniques. These measurements are taken at specific temperatures. Oils that fall into a certain range are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use.


Multi viscosity oils have polymers added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.
10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. The polymers can shear and burn, forming deposits that can cause ring sticking and other problems. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives.


Scope: Tensile tests measure the force required to break a specimen and the extent to which the specimen stretches or elongates to that breaking point. The data is often used to specify material, to design parts to withstand application forces and as a quality control check of materials.
Test Procedure: Place specimens in the grips of the Instron at a specified gage length and pull until failure. The testing speed is determined by the material specification. An extensometer can also be attached to test specimen to determine elongation and tensile modulus


Percent sulfated ash is how much solid material is left when the oil burns. A high ash content will tend to form more sludge and deposits in the engine. Low ash content also seems to promote long valve life. Look for oils with a low ash content.


Percent zinc is the amount of zinc used as an extreme pressure, anti-wear additive. The zinc is only used when there is actual metal to metal contact in the engine. Hopefully the oil will do its job and this will rarely occur, but if it does, the zinc compounds react with the metal to prevent scuffing and wear. A level of 0.11% is enough to protect an automobile engine for the extended oil drain interval under normal use. Those of you with high revving, air cooled motorcycles or turbocharged cars or bikes might want to look at the oils with the higher zinc content. More doesn't give you better protection; it gives you longer protection if the rate of metal to metal contact is abnormally high. High zinc content can lead to deposit formation and plug fouling.


Viscosity Improvers (VIs for short) are fairly large molecules which, at low temperatures, are "curled" into little balls and don't thicken the oil. At higher temperatures, the VIs "uncurl" into long chain molecules which give the oil greater viscosity. Thus, a 5W-30 behaves like a 5W oil at low temperature, and thickens at high temperature into a 30W viscosity.
The drawback of VIs is that because they are long and complex molecules, they are very susceptible to shear as oil circulates within the engine. VI's will suffer breakdown and lose their ability to perform their task. The more VI's an oil uses, the more the oil is subject to this breakdown; losing its ability to provide the necessary viscosity improvement.


Dino oil begins with a base material which is separated from other various crude oil cuts by its boiling range. Various components in crude oil boil off at different temperatures, and material from various ranges goes to a variety of end products such as: kerosene, gasoline, diesel, jet fuel, lube oils, asphalt, etc.
The point being that dino oil base is not a particular chemical species, but a myriad of species, with the only thing in common a similar boiling range. Once this crude cut is split fine enough to be a particular type of lube oil - say automotive engine oil targeted for a particular viscosity range - various additive packages are added. Some of these additive packages are viscosity improvers, corrosion inhibitors and additives to improve filming.


Synthetic oils are developed in the laboratory- from man made organic esters and other synthesized hydrocarbons to provide the exact characteristics desired. These "designer" oils include no impurities, at least when poured from the can. Impurities, of course, can appear during combustion. Synthetic oil is more expensive because it has to be manufactured rather than just separated from a crude cut.
It can be run for longer periods of time between oil changes because it has better thermal stability. The Mobil 1 commercials where they put dino oil and synthetic oil in pans and cook them until the dino oil breaks down are not hype


Better lubrication properties. Longer intervals between oil changes are possible because synthetics suffer less breakdown due to the better base stock used. Usually the synthetics will have a better additive package, allowing the oil to clean better , pump better at lower temperatures, get to critical areas faster among other things.


Cost is one big disadvantage. Also, can't really be used in an older engine due to the nature of synthetics, it tends to be a bit thinner at high temperature. This can exacerbate oil leaks and oil burning. Since the oil is more expensive, it makes the leaks/burning more expensive Another disadvantage is that synthetic oil usually is lower in viscosity at low temperatures. It will have a tendency to drain down faster. You may hear your engine more on cold startup


A blend could give much of the benefits of a synthetic with lower cost. Also a company might sell a blend as a way of attracting folks that are willing to embrace the technology of a synthetic oil, but shy away from the cost of a pure synthetic like Mobil 1.


Viscosity is the internal friction of a fluid or gas. Both have adjacent layers, and when pressure is applied, the friction between layers affects how much the substance will respond to external force. Viscosity, in its simplest form, can be evaluated by the thickness of a substance. A general rule is that gases are less viscous than liquids, and thicker liquids exhibit higher viscosity than thin liquids..


The Flash Point of a chemical is the lowest temperature at which a flame will propagate through the vapour of a combustible material to the liquid surface OR it is the minimum temperature at which the liquid produces a sufficient concentration of vapour above it that it forms an ignitable mixture with air.


Fire point, the temperature at which the flame becomes self-sustained so as to continue burning the liquid (at the flash point, the flame does not need to be sustained). The fire point is usually a few degrees above the flash point.


Cloud point is the temperature where the mixture starts to phase separate and two phases appear, thus becoming cloudy.


Density is mass (m) per unit volume (V), it is essentially, a measurement of how tightly matter is crammed together. The Greek scientist Archimedes discovered the principle of density.


The Pour point of a liquid is the lowest temperature at which it will remain pourable (meaning it still behaves as a fluid).


The carbon residue of a fuel is the tendency to form carbon deposits under high temperature conditions in an inert atmosphere. It may be expressed as Conradson Carbon Residue (CCR) or Micro Carbon Residue (MCR).


The quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize all acidic constituents present in 1 gram of sample. (ASTM Designation D 974)


The quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 gram of sample. (ASTM Designation D 974)


The Value that expresses the weight in milligrams of an alkali needed to neutralize the acidic material in one gram of oil. The neutralization number of an oil is an indication of its acidity.


An element that is present in crude oil and natural gas as an impurity in the form of its various compounds.


A process in which a liquid or vapour mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat.


The aniline point of a petroleum product is the lowest equilibrium solution temperature with an equal volume of freshly distilled aniline. Aniline Point determination is useful in characterizing pure hydrocarbons.


Cetane number or CN is a measure of the combustion quality of diesel fuel via the compression ignition process. Cetane number is a significant expression of diesel fuel quality among a number of other measurements that determine overall diesel fuel quality.
Cetane number is actually a measure of a fuel's ignition delay; the time period between the start of injection and start of combustion (ignition) of the fuel. In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels. Cetane numbers are only used for the relatively light distillate diesel oils.


Ability to tarnish clean copper, indicating the presence of any corrosive sulphur compounds


Wear metals in used oil samples are minute particles of metal suspended in the oil and are formed by friction between moving parts, abrasion or corrosion.
Wear Metal analysis is a trending technique to determine which component is wearing and based on the change in wear metal concentration, the severity of the wear.