Oil Seal Material Guide
The right size makes a seal fit — the right rubber makes it last. Compare the five compounds we stock and pick the one that matches your temperature and media.
The quick comparison
Most applications are covered by NBR. Reach for FKM when it gets hot, EPDM when water or steam is involved, and PTFE when nothing else survives.
| Compound | Temperature | Works well with | Keep away from | Price level |
|---|---|---|---|---|
| NBR · Nitrile | -30 °C … +100 °C | Mineral oils, greases, hydraulic fluids | Brake fluid, ozone, strong sunlight | $ |
| FKM · Viton | -20 °C … +200 °C | Hot oil, fuels, many chemicals | Hot water, steam, ketones | $$$ |
| EPDM | -40 °C … +130 °C | Water, steam, glycol brake fluid | Any mineral oil or grease | $$ |
| PTFE · Teflon | -90 °C … +260 °C | Almost every medium, dry running | — (premium price) | $$$$ |
| VMQ · Silicone | -60 °C … +200 °C | Extreme cold, food-adjacent equipment | Oils and fuels (swells) | $$$ |
| PU · Polyurethane | -30 °C … +80 °C | Hydraulic oil, high pressure, abrasive conditions | Hot water, steam, brake fluid | $$ |
The compounds in detail
NBR — Nitrile rubber
NBR is the workhorse of the sealing world. It resists mineral oils, greases and most hydraulic fluids, it is tough enough for high shaft speeds, and it is the most economical compound there is. If your old seal was a plain black rubber seal in a gearbox or motor, it was almost certainly NBR.
FKM — Viton / fluoro rubber
When the oil gets hot — engine environments, high-speed spindles, anything above 100 °C — FKM is the answer. It also shrugs off fuels, solvents and many aggressive chemicals that would destroy NBR in days. It costs more, but in a hot application it outlasts NBR many times over.
EPDM
EPDM is the mirror image of NBR: excellent in hot water, steam and glycol-based brake fluid, but it swells and fails quickly in any mineral oil or grease. Choose it for pumps moving water or coolant — never for a gearbox.
PTFE — Teflon
PTFE seals resist virtually every chemical, run from -90 °C to +260 °C, and tolerate dry running and very high shaft speeds where rubber lips would burn. The trade-offs are a premium price and a lip that follows shaft runout less willingly than rubber.
VMQ — Silicone
Silicone stays flexible down to -60 °C where other rubbers turn glass-hard, and it is odourless and tasteless, which makes it common around food processing equipment. Its weakness is mechanical strength and oil resistance — it is a specialist, not a generalist.
PU — Polyurethane
Polyurethane is the hardest-working sealing material we stock. It resists extrusion under high pressure, shrugs off abrasion that would shred ordinary rubber, and holds hydraulic oil without complaint. That is why hydraulic cylinder seals — rod seals, piston seals and wipers — are very often PU.
More than shaft seals
The same compounds show up in other sealing products we stock. Two worth knowing:
PTFE gaskets & washers
Flat gaskets and washers cut from pure PTFE sheet. They seal flanged joints, sight glasses and fittings where almost any other gasket material would dissolve — chemically inert from -180 °C to +260 °C, with virtually nothing sticking to them.
Bonded seals (Dowty washers)
A bonded seal is a metal washer with a rubber sealing ring vulcanised into it. Slip it under a bolt head or a hydraulic fitting and tighten — the metal ring prevents over-compression while the rubber does the sealing. Simple, cheap, and reusable within reason.
The rubber element is NBR as standard (FKM on request); the metal ring is available in zinc-plated carbon steel for general use, stainless steel for corrosion-prone or outdoor installations, and brass where galling or spark risk matters.
How to choose in three questions
- What is the seal touching? Oil or grease → NBR or FKM. Water, steam or brake fluid → EPDM. Aggressive chemicals → PTFE. High-pressure hydraulics with abrasion → PU.
- How hot does it get? Under 100 °C → NBR is enough. Up to 130 °C in water → EPDM. Up to 200 °C in oil → FKM. Beyond that → PTFE.
- Any special demands? Extreme cold → VMQ. Dry running or very high speed → PTFE. Nothing special → NBR and save the money.
Still not sure? Send us a photo of the old seal plus a sentence about the machine — we identify seals every day and usually answer within one working day. Contact us →
Common questions
My old seal is black rubber. Is it NBR?
Most likely yes — NBR is by far the most common compound in standard machinery. FKM is often brown or green-marked. When in doubt, tell us the machine type and working temperature and we will confirm.
Can I use FKM instead of NBR “to be safe”?
You can — FKM is backwards-compatible with everything NBR handles, just more expensive. The one exception: if the seal sees hot water or steam, FKM is actually worse than NBR.
Does the compound affect the price?
Yes. NBR is the baseline; EPDM costs slightly more; FKM and VMQ are noticeably higher; PTFE is the premium option. Our search results show the exact price per size and compound before you order.
I have a demanding or unusual application. Can you help?
Yes — tell us the medium, temperature, pressure and shaft speed, and we will recommend a compound and source it if needed. Send your requirements →
Which metal ring should I pick for a bonded seal?
Zinc-plated carbon steel covers most indoor hydraulic work. Choose stainless steel for outdoor, washdown or corrosive environments, and brass where sparking or galling is a concern. The rubber element is NBR by default; ask for FKM if the fitting sees heat or aggressive media.
Six compounds, every metric size
Every seal in our catalog can be filtered by compound, so once you know whether you need NBR, FKM, EPDM, PTFE, VMQ or PU, you see only the sizes that exist in that rubber — with live stock and pricing. We stock the full metric range from 4 mm instrument shafts to 300 mm industrial shafts, shipping from one piece within 48 hours.
For general industrial machinery, NBR remains the practical default; our FKM and PTFE ranges cover hot and chemically demanding service, PU handles high-pressure hydraulics, and for specialised requirements beyond the standard catalog our team sources to order. The range also covers PTFE gaskets and washers, and bonded seals with a choice of zinc-plated steel, stainless steel or brass rings. Tell us what you need →