The Difference Between NBR and FKM O-Rings: Which Rubber O-Ring Is Right for Your Application?

NBR vs FKM O-Rings: A Practical Guide to Material Selection

[2026-07-19] | By Xiamen Jinshun Sealing Technology Co., Ltd. Annie Xu

Choosing an O-ring is not simply about finding the right size. The rubber compound can determine how well the seal performs when exposed to oil, fuel, heat, chemicals, pressure, friction, and outdoor conditions.

Two of the most widely used materials are NBR (nitrile rubber) and FKM (fluoroelastomer). Both are reliable sealing materials, but they are designed for different operating environments.

In simple terms, NBR is a cost-effective choice for many general-purpose oil and hydraulic sealing applications, while FKM is usually preferred when higher temperature resistance, broader chemical resistance, or more demanding service conditions are involved.

For OEM engineers and industrial buyers, the right choice should be based on the actual operating conditions-not simply on material price.

Note: Actual performance varies by compound formulation, hardness, temperature, pressure, fluid, O-ring size, groove design, and operating conditions. The table is intended as a material-selection guide rather than a universal specification.

NBR, or nitrile butadiene rubber, is one of the most commonly used elastomers for industrial O-rings.

Its popularity comes from a practical combination of:

• Good oil resistance
• Good fuel resistance
• Good abrasion resistance
• Good mechanical strength
• Useful low-temperature flexibility
• Competitive material cost

For many industrial applications, an NBR O-ring provides the performance required without the higher material cost associated with premium fluoroelastomers.

Where Are NBR O-Rings Used?

NBR O-rings are commonly selected for:

• Hydraulic equipment
• Pneumatic equipment
• Automotive components
• Engines
• Pumps
• Valves
• Mechanical equipment
• Oil and lubrication systems
• General industrial machinery

If the sealing medium is primarily conventional oil or hydraulic fluid and the operating temperature is within the compound's capability, NBR is often a sensible starting point.

FKM, commonly known as a fluoroelastomer, is a high-performance rubber material developed for more demanding sealing environments.

Its molecular structure gives FKM strong resistance to heat, many oils, fuels, chemicals, weathering, and oxidation.

That makes an FKM O-ring a popular choice when a standard NBR seal may not provide enough temperature or chemical resistance.

Where Are FKM O-Rings Used?

Typical applications include:

• Automotive engines
• Fuel systems
• Petrochemical equipment
• Chemical processing equipment
• High-temperature machinery
• Aerospace-related applications
• Industrial pumps and valves
• Harsh-environment sealing systems

FKM is particularly useful when the seal has to maintain its properties under elevated temperatures or in contact with aggressive fluids.

Both materials can provide excellent oil resistance, but their performance is not identical across every fluid.

NBR

NBR is particularly well known for its resistance to:

• Mineral oils
• Petroleum-based oils
• Hydraulic fluids
• Lubricants
• Many fuels

This is one of the main reasons NBR has become a standard material for hydraulic and automotive sealing.

FKM

FKM provides excellent resistance to many:

• Oils
• Fuels
• Hydrocarbon fluids
• Lubricants
• Chemical mixtures

When the application involves a more aggressive fluid or a combination of high temperature and oil exposure, FKM often provides a wider performance margin.

The important point: Do not select an O-ring based only on the word "oil." The actual fluid composition, temperature, pressure, and exposure time all matter.

Temperature is one of the clearest differences between NBR and FKM.

NBR is suitable for many general industrial applications, but its performance becomes more limited as temperature increases.

FKM is designed for higher-temperature environments and can maintain sealing performance under conditions where conventional NBR may age or lose elasticity more quickly.

For an engineering project, it is better to provide the actual continuous temperature and peak temperature rather than simply asking for a "high-temperature O-ring."

Chemical compatibility is another major difference.

NBR offers good resistance to many common industrial fluids, but it is not designed to handle every chemical environment.

FKM generally provides broader resistance to many aggressive oils, fuels, solvents, and chemicals.

This makes FKM a strong candidate for:

• Chemical processing
• Petrochemical equipment
• Fuel systems
• High-performance automotive systems
• Industrial equipment exposed to aggressive fluids

However, FKM is not universally resistant to every chemical. Certain chemicals and operating conditions can still cause swelling, hardening, or loss of mechanical properties.

For critical applications, chemical compatibility should be checked against the exact medium and compound.

One area where NBR can have an advantage is low-temperature flexibility.

Standard FKM compounds can become less flexible as temperatures fall, while appropriately formulated NBR compounds can provide better low-temperature performance.

This does not mean every NBR compound is better at low temperatures. The actual low-temperature limit depends on:

• Acrylonitrile content
• Compound formulation
• Hardness
• Temperature
• Dynamic or static sealing conditions

If your equipment starts in a cold environment, tell your O-ring manufacturer the minimum operating temperature. Material selection can then be based on the real application rather than a generic material name.

NBR is well known for its good mechanical strength and abrasion resistance.

This makes it useful in applications where the seal experiences:

• Repeated movement
• Mechanical contact
• Wear
• Hydraulic pressure
• General industrial operation

FKM also provides good mechanical performance, but its main selling points are usually its temperature and chemical resistance, rather than maximum abrasion resistance.

For applications where mechanical wear is the dominant concern, NBR can be a very economical option.

Outdoor exposure can be surprisingly demanding for rubber.

Ozone, UV exposure, oxygen, humidity, and repeated temperature changes can gradually degrade unsuitable elastomers.

FKM generally provides better resistance to weathering and ozone than standard NBR.

NBR can still be used outdoors when the design provides adequate protection, but for long-term exposure to harsh weather, FKM may provide a greater performance margin.

Price is another practical consideration for OEM buyers.

NBR generally costs less than FKM because FKM is a more specialized high-performance elastomer.

That does not mean NBR is the "cheap" option. In the right application, NBR can provide an excellent balance of:

performance + availability + manufacturing cost + service life.

FKM becomes more attractive when the additional material cost is justified by the operating environment.

For example, replacing an FKM O-ring with NBR may reduce the component price but create premature seal failure if the equipment operates at high temperature or in a chemically aggressive medium.

A lower purchase price does not necessarily mean a lower total cost.

A simple way to approach the decision is to start with the operating conditions.

This is a starting point, not a substitute for application-specific engineering.

For a production O-ring, the final choice should consider the fluid, temperature, pressure, speed, compression, groove design, shaft condition, and expected service life.

Both materials are widely used in automotive sealing, but the right choice depends on where the O-ring is installed.

NBR

NBR is commonly considered for:

• Hydraulic systems
• General oil seals
• Lubrication systems
• Conventional engine applications
• General-purpose automotive sealing

FKM

FKM is often preferred for more demanding areas such as:

• High-temperature engine compartments
• Fuel systems
• High-temperature oil sealing
• Aggressive fluid environments
• Components exposed to elevated temperatures for long periods

The closer the seal is to a high-temperature or chemically demanding environment, the more important the FKM option becomes.

NBR is a common material for hydraulic O-rings because it combines oil resistance, mechanical performance, and cost efficiency.

For many conventional hydraulic applications, NBR provides an excellent balance.

FKM can be considered when the hydraulic system involves:

• Higher temperatures
• Specialized hydraulic fluids
• More aggressive chemicals
• Long-term heat exposure

The hydraulic fluid should always be identified before choosing the material.

For international OEM buyers, selecting the correct material before tooling and mass production can prevent expensive redesigns later.

When requesting an NBR O-ring or FKM O-ring quotation, provide:

• Inside diameter and cross-section
• Operating temperature
• Maximum temperature
• Minimum temperature
• Sealing medium
• Working pressure
• Static or dynamic application
• Required hardness
• Estimated annual quantity
• Required certifications
• Drawing or physical sample, if available

This information allows a manufacturer to recommend a compound and production specification based on the actual application.

Xiamen Jinshun Sealing Technology Co., Ltd. has specialized in rubber sealing products since 2002.

We manufacture and supply:

• NBR O-rings
• FKM O-rings
• EPDM O-rings
• Silicone O-rings
• Y-seals
• Silicone gaskets
• RO membrane seals
• Silicone tubes
• Custom rubber sealing components

Our manufacturing and quality systems include ISO 9001:2015 and ISO 14001:2015.

For international OEM and industrial customers, we can work from:

• Engineering drawings
• CAD files
• Physical samples
• Existing part numbers
• Dimensional specifications
• Material requirements
• Application specifications

Our raw materials are selected to meet applicable RoHS, REACH, and PAHS requirements. Depending on the product and application, selected products have approvals or certifications including NSF, FDA, LFGB, ACS, KTW-W270, WRAS, and UL.

The right sealing supplier should provide more than a bag of O-rings.

For OEM projects, consistency matters just as much as the initial quotation.

Xiamen Jinshun focuses on:

Material Selection

We help identify whether NBR, FKM, EPDM, silicone, or another elastomer is better suited to the application.

Custom Manufacturing

O-rings can be manufactured according to customer drawings, samples, dimensions, and specifications.

Quality Management

Our company operates under ISO 9001:2015 and ISO 14001:2015 management systems.

International B2B Supply

We work with customers in industrial, automotive, water, sanitary, electrical, machinery, and other sectors.

Long-Term Cooperation

Our goal is not simply to complete one order. We aim to become a stable sealing-component supplier for repeat OEM and industrial programs.

What is the main difference between NBR and FKM O-rings?

NBR is widely used for oil, fuel, hydraulic, and general industrial sealing because of its good oil resistance, abrasion resistance, mechanical performance, and cost efficiency. FKM offers stronger high-temperature and chemical resistance and is generally selected for more demanding environments.

Is FKM better than NBR?

Not necessarily. FKM is better when the application requires higher temperature or broader chemical resistance. NBR can be the better choice when the operating conditions are moderate and cost, abrasion resistance, and oil compatibility are important.

Which is more expensive, NBR or FKM?

FKM is generally more expensive than NBR because it is a higher-performance specialty elastomer. However, the correct material should be selected according to service conditions rather than price alone.

Is NBR good for oil sealing?

Yes. NBR is widely used for sealing mineral oils, petroleum-based oils, hydraulic fluids, lubricants, and many related applications.

Is FKM good for high-temperature applications?

Yes. FKM is widely selected for applications requiring strong resistance to elevated temperatures, especially when heat is combined with oils, fuels, or demanding chemicals.

Which O-ring is better for hydraulic systems?

NBR is a common starting point for conventional hydraulic systems because of its oil resistance, mechanical properties, and cost efficiency. FKM can be considered for higher-temperature or chemically demanding hydraulic applications.

Which O-ring is better for outdoor applications?

FKM generally provides better weathering and ozone resistance than standard NBR. However, the final choice depends on the actual exposure conditions and compound formulation.

Can NBR and FKM be customized?

Yes. Custom NBR and FKM O-rings can be manufactured according to drawings, samples, dimensions, hardness requirements, and application conditions.

How do I choose between an NBR O-ring and an FKM O-ring?

Start with four questions: What fluid will the seal contact? What is the continuous temperature? What is the peak temperature? Is the seal static or dynamic? Then consider pressure, speed, groove design, environmental exposure, and target service life.

Can you manufacture NBR and FKM O-rings for OEM projects?

Yes. Xiamen Jinshun supplies custom rubber O-rings for OEM and industrial applications and can manufacture according to drawings, samples, and agreed specifications.

Choosing the wrong elastomer can lead to swelling, hardening, cracking, leakage, premature wear, and unnecessary replacement costs.

If you are not sure whether NBR or FKM is right for your application, send us the operating conditions.

Please include your:

• O-ring size or drawing
• Working temperature
• Fluid or chemical medium
• Working pressure
• Static or dynamic application
• Required quantity
• Certification requirements

Xiamen Jinshun Sealing Technology Co., Ltd. can help you evaluate the sealing requirements and develop a suitable custom NBR or FKM O-ring solution for your product.

Looking for an NBR O-ring manufacturer, FKM O-ring supplier, or custom rubber O-ring manufacturer in China? Contact Xiamen Jinshun for a quotation and technical evaluation.