Base Oil Refining Process: From Crude Oil to High-Purity Base Stocks

Have you ever wondered what makes lubricants work so well in engines and machines? The answer lies in base oils, the main ingredient that gives lubricants their power. Base oils come from crude oil, synthetic processes, or even renewable sources, and their quality directly affects how smooth, long-lasting, and reliable a lubricant is. Understanding how base oils are made helps us see why some oils perform better than others.

At Fubex Lubricants, we offer high-quality base oils for all types of engines. Enjoy fast shipping, a price match guarantee, and no-questions-asked returns. Need help choosing the right oil? Call us at +971 50 544 9614 — our friendly team is ready to assist!

Awais I., Sales Director, says, “At Fubex Lubricants, we focus on producing high-quality base oils through advanced refining and synthetic processes. Our oils are designed for purity, stability, and top performance, ensuring machines and engines run smoother, longer, and more efficiently in every condition.”

What Are Base Oils?

Base oils are the main ingredient used to make lubricants. The type of base oil you use greatly affects how well the lubricant works. Most base oils come from crude oil, but some are made from synthetic or bio-based sources. The American Petroleum Institute (API) divides base oils into five groups.

Base oils decide important properties of the final lubricant, like thickness (viscosity), how long it lasts (stability), and how much pressure it can handle (load-bearing ability).

For example, a lubricant made with a high-quality base oil can handle heat and chemical changes better than one made with a lower-quality base oil. But even high-quality oil may not carry the same heavy loads if the molecular structure and purity are different.

Because of this, choosing the right base oil is very important. Manufacturers must carefully think about the machine’s working conditions to make a lubricant that keeps the machine running well for a long time.

Base Oil Production Process

Knowing how base oil is made helps us understand its quality and price. There are two main types of base oils: mineral and synthetic. Both start from crude oil, which comes from the earth.

Synthetic base oil is made in a more indirect way. Instead of using crude oil straight, one of its parts is used to create the oil. Mineral base oil, on the other hand, is made directly by refining crude oil.

There are different ways to make base oils, like solvent refining or hydrocracking. These methods make the oil cleaner and affect its grade and quality.

Mineral Base Oil Production Process

Mineral base oil is made and cleaned in the oil refining unit. Two main things go into this unit: lube cuts and deasphalted oil.

Lube cut comes from vacuum towers and goes straight to the refining unit. Deasphalted oil comes from the leftover residue of the vacuum tower, which goes through a deasphalting unit before reaching the base oil unit.

In the oil refining unit, the oil is improved. This makes it better in things like temperature resistance, thickness (viscosity), stability against oxidation, and color. The refining also removes unwanted stuff like aromatics, sulfur, and waxes.

Different refining methods make different grades of base oil. Base oils are divided into five main groups based on things like viscosity, sulfur content, and purity. The first three groups are mineral oils, and their quality gets better from Group 1 to Group 3.

There are two main ways to make base oil in the refining unit: Separation process and Conversion process.

Separation Process

This method uses solvent extraction, which makes a main product and a byproduct. It is an older technique used in refineries built in the early 1900s. It costs less than the conversion process and is mostly used to make low-grade (Group 1) base oils.

It has three steps:

• Solvent Extraction – This step removes aromatic compounds and makes the oil last longer. Solvents like phenol or furfural dissolve the bad compounds. You end up with a main product (base oil) and a byproduct (used for making rubber oils). The main product moves to the next step, dewaxing.
• Dewaxing – Waxes can solidify at low temperatures and make oil less useful. They are removed using methyl ethyl ketone and toluene. The byproduct is pure wax, and the main product is base oil with naphthenic and paraffinic compounds. This usually becomes Group 1 base oil for industrial use.
• Hydrofinishing – For higher-grade oils like Group 2 and 3, the dewaxed oil goes through hydrofinishing to make it even cleaner and better.

Hydrofinishing

Hydrofinishing is a process that cleans the base oil even more. It removes unwanted compounds like sulfur and nitrogen.

This happens through a chemical reaction using a catalyst and hydrogen at high temperature and pressure. The higher the temperature and pressure, the better the base oil becomes.

After hydrofinishing, the oil has a higher viscosity index (VI), better stability against oxidation, a lighter color, and less sulfur. This high-quality oil is used in sensitive machines, airplanes, ships, and advanced industries.

Conversion Process

The conversion process changes unwanted molecules into good ones using catalysts, hydrogen, heat, and pressure. A great thing about this process is that no byproducts are wasted, so 100% of the input becomes high-quality base oil.

This process has three steps to make Group 2 and 3 base oils:

• Hydrocracking – This breaks large, complex molecules into smaller, simpler ones using high heat and pressure. It makes the oil more uniform and easier to use.
• Hydroisomerization – Also called hydrodewaxing, this changes waxy compounds into isoparaffins, which are liquid at room temperature and freeze at much lower temperatures. This lowers the oil’s pour point (the lowest temperature it can flow) and makes it better for cold weather. It also improves oxidation resistance.
• Hydrotreating – This step removes any remaining unwanted compounds like sulfur and nitrogen. It also strengthens the oil’s chemical bonds using more hydrogen, giving it high stability and making it ready for advanced industrial use.

Synthetic Base Oil Production Process

Synthetic base oils are made artificially using chemical reactions. In this process, new molecules are created so the oil has the best qualities for high performance.

Even though it’s made artificially, the starting material still comes from petroleum (like ethylene) that is chemically and physically changed.

The way the oil is made and the additives used are different for each company, so every manufacturer has its own special formula.

Base Oil Properties

Base oils have four main properties that decide how well they will work:

• Pour Point – This is the lowest temperature at which oil can still flow or be poured.
• Viscosity – This is how thick or sticky the oil is. For example, honey is more viscous than water.
• Viscosity Index (VI) – This shows how much the oil’s thickness changes with temperature. A high-VI oil changes less with temperature and works well in both hot and cold conditions. Multi-grade engine oils need high-VI base oils to start with.
• Purity – Oils must have very low amounts of sulfur, nitrogen, and other unwanted compounds to work properly.

The main thing to remember is that base oils give most of the performance of the final lubricant. Choosing the right base oil is very important to keep metal parts moving smoothly and make machines work their best.

But base oils are only part of the formula. Scientists and engineers also use special additives. The final performance of any lubricant comes from the combination of base oils, additives, and expert knowledge.

Refining Process

Base oils are made in different thickness levels (viscosity grades) at the refinery. This helps produce oils that meet the ISO and API standards.

Here are the main steps:

• Atmospheric Distillation – This is the first step. It separates fuels like gasoline and diesel from crude oil. The separated parts are called distillates.
• Vacuum Distillation – This separates the heavier parts of crude oil that can’t be distilled at normal pressure. It helps get the base oil’s initial thickness and flash point. It also produces the four main viscosity fractions that are used to make finished oils.
• Refining – This step removes unwanted chemical structures from the base oil. This makes the oil last longer and improves its temperature and viscosity properties. There are three main refining methods:
  • Acid/Clay Refining – An old method using sulphuric acid or clay to clean the oil. It improves color and stability but creates a lot of waste, so it’s mostly replaced now.
  • Solvent Extraction – This removes unwanted rings and aromatic compounds using liquids like phenol, furfural, or sulfur dioxide. After this, the oil is dewaxed and sometimes hydrofinished to improve color and stability.
  • Catalytic Hydrogenation (Hydrotreating) – This uses hydrogen, heat, pressure, and a catalyst to remove unwanted compounds. It creates very high-quality oil with minimal waste. There are three types:
  • Hydrofinishing – Mild cleaning to remove leftover impurities.
  • Hydrotreating – Improves color, smell, stability, and water separation.
  • High-pressure Hydrogenation (Hydrocracking) – Completely removes unwanted compounds and converts them into valuable branched paraffin oils.
• De-asphalting – Removes heavy asphalt residues from the oil.
• De-waxing – Removes wax to improve performance in cold temperatures.
• Blending – The final step. Different base oils are mixed together to get the right viscosity. Additives are added so the final oil can lubricate machines properly.

History of Base Oils

People have been using oils as lubricants for a very long time. In ancient times, they used animal fats and vegetable oils to reduce friction and wear in machines like chariots and water mills.

When the industrial era began, people started using mineral oils from crude oil. These worked better and lasted longer than animal-based oils.

The modern base oil industry started in the early 20th century. Refining methods were developed to make high-quality base oils from crude oil. Over time, technology improved, and synthetic and bio-based oils were created with even better properties.

Today, base oils are made all over the world and supplied to lubricant manufacturers everywhere. Companies compete to make better oils while also reducing environmental impact.

Here are some important milestones in the history of base oils:

• 1859: The first commercial oil well was drilled in Pennsylvania, USA. This started the use of petroleum-based lubricants.
• 1868: The first patent for lubricating oil in the USA is granted for oil made from sperm whale oil and tallow.
• 1869: The first lubricating oil refinery is built in Cleveland, Ohio, USA. It produced kerosene and lubricating oil from crude oil.
• 1902: The first hydrocracking process was developed to make high-quality base oils.
• 1920s: Solvent refining is developed, making cleaner and better oils.
• 1940s: Synthetic base oils like PAOs and PAGs are created.
• 1990s: Bio-based oils are made from renewable sources like animal fats and vegetable oils.
• 2010s: New refining processes improve environmental performance, like hydroisomerization and isodewaxing.

Base oils are very important because they form the foundation of lubricants. Their quality affects how well the finished lubricant works.

The base oil industry is a key part of the global economy, and continued innovation will keep improving oils for many industries.

Final Takeaways

Base oils are the heart of every lubricant. From ancient animal fats to modern synthetic and bio-based oils, they keep machines running smoothly. How base oils are made—through refining, hydrofinishing, or chemical conversion—directly affects their quality and performance.

Choosing the right base oil is very important for viscosity, stability, and load-bearing ability, and additives help make the final lubricant even better. The base oil industry continues to evolve, creating cleaner, stronger, and more efficient oils that keep our world moving.

FAQs

Q1: How is base oil made from crude oil?

Group I base oils are made from parts of crude oil. During the process, unwanted molecules like paraffin waxes and aromatics are removed. Paraffin waxes are taken out because they solidify at high temperatures and can affect how the oil flows and works.

Q2: What is Type 4 base oil?

Type 4 base oils are called polyalphaolefins (PAOs). They are synthetic oils made through a process called synthesizing. These oils can handle a wide range of temperatures, making them perfect for very cold or very hot conditions.