HNBR O-Rings for Automotive Applications
Hydrogenated nitrile for under-hood heat, ozone, E10 gasoline and transmission fluid — the upgrade path from NBR when temperatures exceed +120°C.
HNBR (hydrogenated nitrile) is the workhorse automotive elastomer when NBR's +120°C ceiling is insufficient but full FKM cost is not justified. HNBR retains NBR's petroleum oil and fuel compatibility while adding heat resistance to +150°C, excellent ozone and weathering resistance, and improved resistance to E10 ethanol blends and sour gas environments.
Common automotive HNBR sealing points
- Oil filter housing and drain plug seals — hot engine oil to +150°C
- Power steering pump and rack seals — ATF and mineral oil at elevated temperature
- Transmission cooler and valve body seals — automatic transmission fluid
- Fuel system (port injection) — E10 gasoline and diesel where FKM is not required
- A/C compressor service ports — refrigerant and PAG oil (verify compound)
HNBR is not a drop-in for all FKM fuel applications. Direct injection above 150 bar, E85 flex-fuel and continuous +170°C under-hood locations typically require FKM for fuel systems. Use HNBR where port injection, moderate heat and cost efficiency align.
Explore: automotive O-rings hub, fuel injector seals, automotive A/C, automotive industry page. Full specs: HNBR product page.
Why HNBR for This Application
Under-hood heat resistance
Continuous +150°C with improved compression set versus NBR — suited for oil filter, power steering and transmission seals near the engine.
E10 ethanol compatibility
Hydrogenated backbone resists ethanol permeation and oxidative attack better than standard NBR in modern gasoline blends.
Ozone & weathering
Saturated chain structure eliminates ozone cracking — critical for exterior engine bay and under-chassis locations.
Cost vs FKM
Typically 40–60% lower cost than FKM for port-injection fuel and hot-oil service where FKM temperature margin is not needed.
Common Sizes
| Size | Typical Use |
|---|---|
| Oil filter large-diameter (custom) | Spin-on and cartridge filter housing gaskets — quote ID × CS |
| AS568 -111 to -116 (2.62 mm CS) | Power steering line and sensor port seals |
| Metric 8×2 – 12×2 mm | Fuel rail and injector seals on port-injection engines |
| Drain plug crush seals | Copper vs elastomer — many OEM drain plugs use bonded HNBR 70 |
| AS568 -012 to -018 (1.78 mm CS) | A/C service port and small sensor face seals |
Related Application Guides
FAQ
HNBR or FKM for fuel injector O-rings?
FKM is preferred for direct injection and high-performance engines. HNBR 70–80 Shore A is acceptable for many port-injection systems on E10 gasoline at lower cost.
Can HNBR replace NBR in all automotive seals?
HNBR is a direct upgrade for hot-oil and under-hood locations. Standard NBR remains fine for cold fuel lines, interior HVAC and low-temperature locations where +120°C is never reached.
Is HNBR compatible with automatic transmission fluid?
Yes. HNBR resists ATF and most mineral-based transmission fluids to +150°C — common for valve body and cooler circuit seals.
What hardness for oil filter housing seals?
HNBR 70 Shore A is standard for filter housing o-rings. Ensure the seal is seated in a clean groove — filter housing leaks are often caused by pinched or twisted installation, not material failure.
Does HNBR resist ozone under the hood?
Yes. HNBR's saturated backbone provides excellent ozone resistance — unlike standard NBR, which cracks in ozone-exposed engine bay locations within months.
MOQ for aftermarket automotive HNBR seals?
MOQ 1 piece for custom sizes. Popular oil filter and power steering sizes are stocked for 3–5 day dispatch.
Request HNBR automotive O-rings
Share the vehicle system (engine oil, fuel, transmission, A/C), fluid type and size. We recommend HNBR grade and hardness with lead time and pricing.