Oil- and Fuel-Resistant Rubber: Best Materials for Gasoline, Diesel and Hydraulic Oil
What's the best oil- and fuel-resistant rubber? Compare NBR, FKM and polyurethane for gasoline, diesel and hydraulic oil.
About this article
This article was prepared by the technical team at Hamta Polymer Zayandeh Rood Industries. Contact our specialists for application guidance and the right option for your industrial need.
What's the best oil- and fuel-resistant rubber? Compare NBR, FKM and polyurethane for gasoline, diesel and hydraulic oil.
# Oil- and Fuel-Resistant Rubber: Best Materials for Gasoline, Diesel and Hydraulic Oil
Oil- and fuel-resistant rubber refers to materials that stay stable in continuous contact with petroleum products — no swelling, no softening, and no loss of sealing force. The most common option is NBR (nitrile), an economical and reliable choice for most gasoline, diesel, and hydraulic oil applications. At high temperatures or where chemicals are also present, FKM (Viton) performs better. This guide breaks down the differences between these materials and how to pick the right one based on your fluid.
This article is part of our Complete Guide to Rubber Seals; if you're not familiar with the basic O-ring and seal types, start there first.
Table of Contents
- Why ordinary rubber fails on contact with oil and fuel
- The main oil- and fuel-resistant materials
- Quick technical specification chart
- Applications in automotive, hydraulic and petrochemical industries
- How to choose based on fuel or oil type
- Common selection mistakes
- FAQ
Why Ordinary Rubber Fails on Contact With Oil and Fuel
General-purpose elastomers like natural rubber (NR) or EPDM have a non-polar molecular structure that rapidly absorbs petroleum-based hydrocarbons (gasoline, diesel, oil). That absorption causes the part to physically swell, lose tensile strength, and eventually lose its sealing force. That's why any part sitting in the fuel or oil path — from a fuel pump O-ring to a hydraulic reservoir gasket — needs a polar, oil-resistant material.
The Main Oil- and Fuel-Resistant Materials
NBR (Nitrile) — the economical, high-volume choice: thanks to its strong cost-to-performance ratio, nitrile rubber is the most widely used material in the automotive and hydraulics industries. NBR resists mineral oils, grease, and standard gasoline well, but performance drops above roughly 100°C or when exposed to fuels with a high ethanol content.
FKM (Fluoroelastomer / Viton) — for high temperature and aggressive fuels: at high temperatures (above 150°C) or in contact with fuels containing chemical additives, FKM is the more reliable choice. Its higher cost is usually justified in demanding industrial projects (petrochemical, aerospace).
Polyurethane (PU) — high abrasion resistance under hydraulic pressure: for hydraulic parts that face both oil exposure and mechanical wear/high pressure (like hydraulic piston seals), polyurethane offers a longer service life than NBR thanks to superior abrasion resistance; see the full comparison in our guide on the differences between rubber and polyurethane.
Quick Technical Specification Chart
| Property | NBR (Nitrile) | FKM (Viton) | Polyurethane (PU) |
|---|---|---|---|
| Resistance to gasoline/diesel | Good to excellent | Excellent | Fair to good |
| Resistance to hydraulic oil | Excellent | Excellent | Excellent |
| Max continuous operating temp. | 100–120°C | 200–220°C | 80–90°C |
| Abrasion resistance | Fair | Fair | Excellent |
| Relative cost | Low | High | Medium to high |
Applications in Automotive, Hydraulic and Petrochemical Industries
In the automotive industry, NBR is the standard for fuel pump gaskets, injector O-rings, and standard fuel hoses. In industrial hydraulic systems, choosing between NBR and polyurethane usually comes down to system working pressure and piston speed. In petrochemical industries, where temperature and pressure run much higher and fuel may contain sulfur or other chemical compounds, FKM is the industry standard.
How to Choose Based on Fuel or Oil Type
- Standard gasoline and diesel at ambient temperature: NBR is sufficient and the most cost-effective option.
- High-ethanol fuels (E85 and similar): FKM is recommended for its better resistance to alcohol-induced swelling.
- Hydraulic oil under high pressure and speed: polyurethane delivers longer service life thanks to superior abrasion resistance.
- Environments above 150°C (near engine or exhaust): only FKM guarantees adequate stability.
Common Selection Mistakes
- Using NBR in high-temperature environments without checking the data sheet, leading to premature hardening and cracking.
- Ignoring the effect of modern fuel additives (like ethanol), which are incompatible with older NBR formulations.
- Choosing polyurethane for high-temperature environments, when this material has a lower heat limit than FKM.
FAQ
Is NBR suitable for today's ethanol-blended gasoline?
For standard gasoline, yes. But for fuels with a high ethanol content, standard NBR formulations can swell over time, and FKM is the safer choice.
What's the main difference between NBR and FKM?
NBR is cheaper and suitable for moderate temperatures and standard oil/fuel. FKM costs more but offers much better resistance at high temperature and against aggressive chemicals.
Why is my hydraulic seal wearing out faster than expected?
If the system runs at high pressure and piston speed, NBR may not be the right choice — polyurethane offers a longer service life thanks to its superior abrasion resistance.
Can a single material resist both oil and acid?
FKM is one of the few options that holds up well against both oil/fuel and most acids; see the details in our chemical and acid resistance guide.
What's the max working temperature for NBR in contact with engine oil?
Typically around 100–120°C, but the exact figure depends on the compound's precise formulation and should be confirmed with the manufacturer's data sheet before ordering.
Sources & References
This guide draws on the industrial standards ASTM D2000 and ASTM D471 and general technical guidance from international seal manufacturers including Parker Hannifin and Trelleborg Sealing Solutions.
Summary
For most standard automotive and hydraulic applications at moderate temperature, NBR is the standard, cost-effective choice. In high-temperature conditions, alcohol-blended fuels, or petrochemical environments, FKM is the more reliable investment; and for hydraulic parts facing high wear and pressure, polyurethane delivers the best service life. If you're not sure which material fits your project, our technical team offers a free consultation and price quote.
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