FKM O-Rings for Fuel Systems
Premium fluoroelastomer seals for injectors, fuel rails, pumps and EVAP systems — resist ethanol blends, aromatics and under-hood heat to +200°C.
Fuel system O-rings must survive aggressive hydrocarbons, oxygenated blends and rising under-hood temperatures. FKM (Viton / FPM fluoroelastomer) is the default premium choice when port- or direct-injection pressures, aromatic fuels, or continuous service above +120°C push standard NBR beyond its limits.
Where FKM seals fuel systems
- Fuel injectors — upper rail seal and lower manifold seal in GDI/DSI and PFI systems
- Fuel rails and crossovers — static face seals at 30–200 bar
- High-pressure pumps — plunger and valve seals in modern direct-injection systems
- EVAP and tank vent lines — low-permeability seals for emissions compliance
FKM's low fuel vapor permeability (roughly 50–100× lower than NBR) makes it essential for evaporative emissions hardware. For cost-sensitive port injection on E10 gasoline, HNBR O-rings for automotive may suffice — but direct injection, turbocharged engines and E85 service typically require FKM 75–90 Shore A.
See our dedicated guides for fuel injector O-rings and automotive fuel systems. For a material overview, visit the full FKM product page.
Why FKM for This Application
Fuel & aromatic resistance
FKM resists gasoline, diesel, E10/E85, biodiesel and aromatic additives where NBR swells 25–35% in reference oil at elevated temperature.
High-temperature headroom
Continuous service to +200°C with compression set ≤ 20% at 200°C — critical for turbocharged and direct-injection under-hood locations.
Low fuel permeability
Mandatory for EVAP canister, tank vent and emissions-related seals where hydrocarbon vapor loss is regulated.
Grade options
Standard Type 1/2 for general fuel service; GF low-temp grade to -40°C for cold-climate starts; GFLT for maximum chemical resistance.
Common Sizes
| Size | Typical Use |
|---|---|
| Metric 6×1.5 – 14×2.5 mm | Fuel injector upper/lower seals (common Asian/European injectors) |
| AS568 -006 to -016 (1.78 mm CS) | Small fuel line and sensor face seals |
| AS568 -110 to -116 (2.62 mm CS) | Fuel rail fittings and medium-pressure static joints |
| AS568 -210 to -214 (3.53 mm CS) | Large fuel pump and filter housing seals |
| ISO 3601 metric | European fuel system hardware and aftermarket replacements |
Related Application Guides
FAQ
Is FKM the same as Viton for fuel O-rings?
Yes. Viton is a trade name for FKM fluoroelastomer. FKM, FPM and fluoroelastomer refer to the same polymer family used for fuel-resistant O-rings.
FKM or HNBR for E10 gasoline?
HNBR 70–80 Shore A works for many port-injection systems on E10. Specify FKM when temperatures exceed +120°C, direct injection pressures apply, or E85/biodiesel blends are present.
What hardness for direct-injection fuel seals?
FKM 90 Shore A is common for GDI/DSI pressures above 150 bar without backup rings. FKM 75 Shore A suits lower-pressure rail and line seals where groove fill and conformability matter more.
Can FKM O-rings handle biodiesel?
Standard FKM resists B20 biodiesel blends well. For high-biodiesel (B100) or aggressive fatty-acid exposure, confirm compound qualification with ASTM D471 immersion data for your specific blend.
What is the temperature limit for FKM fuel seals?
Continuous +200°C; short excursions to +230°C. GF low-temperature grades extend cold flexibility to -40°C for arctic fuel system service.
Do you supply AMS-R-83485 traceable FKM?
Yes. Aerospace and motorsport fuel system grades with batch certificates of conformance are available on request. MOQ from 1 piece for custom sizes.
Need FKM fuel system O-rings?
Send fuel type, temperature, pressure and size — we confirm compound grade and quote AS568, ISO 3601 or custom metric sizes with 3–7 day lead time on stocked compounds.