An overview of crude oil, including its constituent hydrocarbons and refinement outputs

Learn about the chemical refinement of crude oil, from cracking to reforming and blending

Just as an organism's digestive system can break down complex molecules in food into simple sugars that cells can use, cracking uses catalysts and other chemicals to break apart large hydrocarbons in crude oil into smaller molecules. These can then be chemically reshaped, combined, or purified into useful petroleum products.

Crude oil is the type of oil used to create fuel like gasoline, heating oil, and more

Technically speaking, crude oil is unrefined petroleum. This article dives into the different ways it’s categorized (by density, sulfur content, and origin), and how the combinations of these types of oil are used.

View the 45 gallons of refined products created from each 42-gallon barrel of crude oil

More than 85% is refined into fuels, such as gasoline and diesel, while about 10% is converted into raw materials for plastics, synthetic rubbers, and other essential products, such as lubricants. Because the majority of these products are less dense than the starting crude oil and additional inputs are introduced during the refining process, there is a processing gain of three gallons.

An animated visualization of the distillation of crude oil into petroleum products

When crude oil is boiled, its constituent hydrocarbons turn into steam and rise through a distillation tower, where temperature decreases with height. Because different chemical vapors cool back into liquids at distinct temperatures, hydrocarbons naturally sort themselves by boiling point and can then be processed separately into distinct outputs.

The ins and outs of oil refining

The oil industry is broken up into the upstream, midstream, and downstream segments, and oil refining is part of the latter. “Downstream” refers to companies like Standard Oil that are converting crude oil into a finished product.

View a sample of objects surprisingly derived from crude oil, including chewing gum and lipstick

Crude oil processing produces a variety of fuels and the building blocks for plastics, but it also distills out the hydrocarbons used to make aspirin, Teflon, vinyl, crayons, candles, Tupperware, roofing shingles, asphalt pavement, hair dye, anesthetics, food-grade lubricants, polyester, synthetic rubber, and resins for items like dentures.

A look at types of crude oil, distinguished by properties like heaviness and sweetness

API gravity is a unit that describes how heavy or light a crude oil sample is based on its density, with higher values indicating lighter, more valuable oil that requires less processing. The sweetness of crude oil refers to the amount of sulfur it contains, where sour crude oil requires more extensive treatment to remove the more abundant sulfur and sweeten it.

How microorganisms transformed into crude oil over millions of years

Despite the misconception that oil comes from dinosaurs, the nonrenewable resource forms when tiny organisms are subjected to high pressure and high temperature while buried under layers of sediment over tens to hundreds of millions of years. During this time, they become a mixture that is almost entirely hydrocarbons, which can be harnessed and refined.

How crude oil is split across oil markets based on geographic origin

Brent, West Texas Intermediate, and Dubai are the three crude oil classes and differ in terms of typical refinery uses, density, sulfur content, and suitability for financial benchmarking. Brent, which originates in the North Sea, is traders' go-to benchmark, in part, because it is easily shipped and politically stable, and used to price most of the crude sold internationally.

Demystifying the claim that crude oil is inorganically created and a renewable resource

The abiogenic petroleum theory holds that fossil fuels originate in Earth's mantle and are constantly replenished, rather than formed by microorganisms over millions of years. While inorganic chemical processes can produce simple hydrocarbons, the range of complex molecules found in crude oil suggests an origin from a diverse set of organisms. Isotope analyses of these molecules also support the model that they originated from living things that preferentially take up certain isotopes over others.

The price of crude oil accounts for roughly half of the price displayed at the gas pump

While the price of crude oil has the largest impact on the price of gas, the cost of refinement, taxes, and distribution jointly make up nearly half of how gas is priced. Because of the many factors that influence the price of gas, eliminating taxes during expensive periods might not effectively lower prices.

Watch how plastic products are molded from pellets that began as crude oil

Polyethylene and other plastics are formed by combining ethylene and propylene, which are produced through refining crude oil. These plastics are broken down into pellets called nurdles, or mermaid tears, which are melted and molded to manufacture countless products.

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.

A guide to crude oil and natural gas extraction, from rig site preparation to land restoration

Requirements for traffic plans, access roads, and noise barriers vary by state and local laws, but once the rig site is prepared, the rig is assembled and digs a well that is then encased in steel and cement to protect groundwater reservoirs. After drilling and testing the extraction pipe, fracking fluid is injected into the rock to create cracks where crude oil resides, allowing it to be pumped out.

Explore a timeline of US dependence on crude oil from 1850 to 2023

Oil dependence began with the rise of oil as a commodity, followed by an era of geopolitical competition for the resource after World War II. The domestic fracking boom, which started around 2006, was driven by a desire to reduce the nation's dependence on international adversaries for energy.

A chemical overview of water, whose uncommon properties help sustain life on Earth

The uneven distribution of charge in water molecules allows them to bond to each other and to surfaces, enabling them to move against gravity, including up plants through roots and stems. These bonds also keep water in a liquid state over a wider temperature range and make it less dense as it freezes. This causes ice to float and form an insulating layer for underwater ecosystems, from which all life originated.

Internal-combustion engines convert fuel into motion using controlled explosions

Gasoline engines mix fuel and air, compressing it and igniting it to create thousands of tiny explosions that push pistons up and down. This movement spins the crankshaft, which moves a vehicle's wheels.

Review the health effects of living near oil refineries, including increased respiratory risks

An analysis of 54 studies published between 1977 and 2024 in 15 international regions found evidence that proximity to refineries increased the risks of leukemia, asthma, bronchitis, and respiratory symptoms. Several studies also identified worse cardiovascular function in children and adults living near refineries, alongside other acute and chronic health impacts.

An overview of atomic composition, scale, and structure, which is almost all 'empty' space

It takes about 500,000 carbon atoms lined up next to one another to span the thickness of human hair, and over 99.9994% of the mass of each is contained in the nucleus. About 99.999999999999% of an atom's volume lies outside this nucleus, where electrons exist in clouds of probability. Removing these clouds, the Empire State Building would be the size of a rice grain.

Explore OPEC’s official webpage

OPEC’s official website offers a comprehensive hub for its core work—featuring press releases, monthly and statistical reports, digital publications like the World Oil Outlook and Annual Statistical Bulletin, and other research center materials.

The industrial methods for recovering helium, including filters and cryogenic separation

Membranes with microscopic pores of varying sizes can be used to selectively filter out components of natural gas, including helium, which can then be concentrated. Because helium requires the lowest temperature of all elements to condense into a liquid, extracted natural gas can also be cooled until only helium remains as a gas.

An explanation of the Calvin cycle, including why it needs to run six times to create glucose

Each run of this second phase of photosynthesis begins with a five-carbon molecule called RuBP, which gains an additional carbon atom when carbon dioxide (CO₂) is attached. Across six cycles, the six six-carbon molecules—36 carbon atoms in total—are processed into 12 three-carbon sugars, which can be used to generate glucose, and six RuBP molecules, enough for each cycle to restart.

An overview of hydropower

Hydropower, or the use of the natural flow of moving water to generate electricity, is one of the oldest and largest sources of renewable energy.

Graphite is a powerful conductor and heat-resistant material

Graphite can withstand temperatures of more than 3,000 degrees Celsius, allowing it to contain molten metal in steel production. Rosalind Franklin identified which carbon compounds become graphite and laid the groundwork for their use in industrial applications.

An overview of Linux, from the foundational program to its related operating systems

The Linux kernel, which bridges hardware and software, serves as the basis for many fully customizable operating systems, whose components can be modified or removed to optimize performance or reduce bloat on devices with limited resources. This has made these OSes useful for low-power devices like smart thermostats, as well as for powerful supercomputers that require computational efficiency.

Hydrogen vehicle adoption has struggled due to high costs and stiff EV competition

Despite features like fast refueling and zero emissions, hydrogen vehicles face significant hurdles in affordability and infrastructure. As of 2025, there are about 200,000 electric vehicle charging stations compared to fewer than 100 hydrogen fuel ones.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

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