Comparison guide
EPDM vs Fluorocarbon (FKM) O-Rings
EPDM and Viton® (FKM) divide by what the seal touches: EPDM for water, steam, glycol brake fluid and phosphate-ester hydraulic fluid, FKM for petroleum oils, fuels and solvents. EPDM must never see petroleum oil, and standard FKM degrades in steam. On the Parker® O-Ring Handbook (ORD 5700) ranges, standard EPDM runs -57 C to 150 C, with steam compounds to 204 C, and standard FKM -26 C to 204 C.
EPDM and Viton rarely compete for the same job: each fails exactly where the other excels, and the media decides. EPDM (ethylene propylene) is the water-side material: hot water, steam, glycol brake fluid, phosphate-ester hydraulic fluid, acids, ketones and outdoor service. Viton (FKM) is the oil-side material: petroleum oils, fuels, aromatics and chlorinated solvents at temperature. On the Parker O-Ring Handbook (ORD 5700) ranges, standard EPDM runs -57 C to 150 C (-70 F to 302 F) with steam compounds to 204 C, and standard FKM runs -26 C to 204 C (-15 F to 400 F).
EPDM and Viton compared
| Factor | EPDM | Viton (FKM) | Source |
|---|---|---|---|
| Continuous temperature range | -57 C to 150 C (-70 F to 302 F) | -26 C to 204 C (-15 F to 400 F) | Parker ORD 5700 |
| Special compounds | Steam grades to 204 C (400 F) | Low-temperature grades to -46 C | Parker ORD 5700 |
| Water, steam, glycols | Excellent | Limited in standard grades | Parker ORD 5700 section 2.2 |
| Petroleum oils and fuels | Destroyed; swells and fails | Excellent | Parker ORD 5700 section 2.2 |
| Glycol brake fluid | Excellent | Not recommended | Parker ORD 5700 section 2.2 |
| Phosphate-ester hydraulic fluid (Skydrol®) | Excellent | Not recommended | Parker ORD 5700; NAS1613 |
| Ketones and polar solvents | Good | Poor | Parker ORD 5700 |
| Aromatics and chlorinated solvents | Poor | Excellent | Parker ORD 5700 |
| Acids | Good, dilute and hot | Acid grades for concentrated acid at room temperature | Parker ORD 5700 section 2.2 |
| Ozone and weathering | Excellent | Excellent | Parker ORD 5700 |
| Low-temperature flexibility | Excellent | Limited | Parker ORD 5700 |
| Potable water and food listings | NSF/ANSI 61 and FDA listed EPDM compounds exist, such as Parker E3609-70 | No listing on a generic FKM; the grade sheet governs | Parker E3609-70 drinking water and medical O-ring product page |
Which material for which application?
| Application | Usual callout | Why |
|---|---|---|
| Steam line, sterilizer, clean-in-place system | EPDM | Steam grades to 204 C; FKM degrades in steam |
| Potable water fitting, pump, valve | EPDM | NSF/ANSI 61 listed compounds are EPDM |
| Brake caliper, master cylinder (glycol fluid) | EPDM | Brake fluid is butyl or EPDM only |
| Aircraft hydraulics on Skydrol | EPDM to NAS1613 | Phosphate ester attacks FKM and nitrile |
| Engine oil, gearbox, fuel system | Viton | Oil destroys EPDM |
| Chemical processing with solvents and aromatics | Viton | EPDM swells in non-polar solvents |
| Acetone or MEK service | EPDM | Ketones swell FKM heavily |
| Outdoor irrigation, cooling tower, roof equipment (no oil) | EPDM | Weathering resistance at lower cost |
| Mixed oil-and-water system | Viton | Any oil present rules EPDM out |
| Hot service above 150 C with oil present | Viton | Above EPDM's standard ceiling |
Where EPDM is the usual callout
The media is water, steam, glycol brake fluid or phosphate-ester fluid, or the seal lives outdoors, and petroleum products are guaranteed absent. The EPDM guide covers the compliance listings and the aerospace callout.
Where Viton is the usual callout
The media is oil- or fuel-based, or chemically aggressive, especially at temperature. A mixed system that sees both oil and water usually lands on Viton, or on a nitrile grade at moderate temperature. The Viton guide covers the specifications.
What the print might say
Prints name documents, not trade names. Statuses are read from the SAE and DLA ASSIST document records and the Parker E3609-70 datasheets.
| Callout | Material | Part standard or example | Note |
|---|---|---|---|
| NAS1613 | EPDM for phosphate-ester hydraulic fluid | Parker E0515-80 (Revision 2), E1267-80 (Revision 5), Table 8-4 | The aerospace EPDM O-ring document (Skydrol systems) |
| NSF/ANSI 61, NSF/ANSI 51 | EPDM compounds listed for drinking water and food equipment | Parker E3609-70 | Compliance belongs to the compound |
| FDA 21 CFR 177.2600, USP Class VI | Compliant compounds; an FKM grade carries its own sheet | Parker E3609-70 (EPDM) | See the FDA guide |
| MIL-P-82744 | EPDM, 80 A | Parker ORD 5700 Table 8-3 (E0515-80) | Otto fuel service |
| AMS7276 | FKM, 70 to 80 A | AS3209, AS3208, AS83248/1 | The current aerospace fluorocarbon O-ring; see the AMS7276 guide |
| M83248/1, M83248/2 | FKM, 75 A and 90 A | legacy MIL part family | Supplied to AMS7276 and AMS7259; see the M83248 guide |
| ASTM D1418 designations | EPDM, FKM | none | The family letters used on datasheets and D2000 callouts |
How each material fails, and what it looks like
The Parker handbook's failure-mode table makes the two easy to tell apart after the fact. An EPDM ring that touched petroleum oil comes out enlarged, soft and gummy, often too big to go back in its groove. A Viton ring in steam or hot water comes out hardened and cracked; in a ketone it comes out swollen. Both take a flat-sided set when over-squeezed at temperature (see the compression set guide), and both resist ozone, so weather cracking points at nitrile rather than at either of these two.
The one rule that catches people
The Parker handbook flags EPDM plus petroleum oil. An EPDM seal that touches even a small amount of mineral oil, grease or fuel swells, softens and fails, and the failure looks like an oversize, gummy ring. A simple way to remember it: nitrile resists oil but not weather, EPDM resists weather but not oil, and FKM handles both. When in doubt about oil, do not use EPDM. The chemical compatibility guide covers the media families in more detail.
Gland and installation notes for the pair
Both materials use the same AS568 sizes and the same O-ring groove design rules from the Parker handbook: static squeeze no more than about 30 percent for most elastomers and dynamic about 16 percent, gland fill of 60 to 85 percent with 75 percent the optimum, and no more than about 5 percent assembled stretch (sections 3.5 to 3.7) (the squeeze guide has the numbers). Two practical differences follow from the chemistry. The assembly lubricant must match the material: a petroleum grease that is harmless on Viton will start an EPDM ring swelling before the machine runs, so EPDM is assembled with a silicone or glycol-based lubricant. And a system flushed or tested with a petroleum fluid before it goes into water service will have destroyed its EPDM seals before commissioning; specify the flush fluid with the seal. In steam service, a peroxide-cured EPDM holds its squeeze longer than a sulfur-cured one, and the compression set guide explains why that matters at temperature.
Viton is a trademark of The Chemours Company; Parker is a trademark of Parker Hannifin Corporation; Skydrol is a trademark of Solutia Inc. No affiliation or endorsement is implied.
Sources
- Parker O-Ring Handbook ORD 5700, section 2.2, read 2026-09-14
- Parker O-Ring Handbook ORD 5700, Table 8-3 (page 8-4), read 2026-09-24; Section VII steam ratings, read 2026-09-25
- Parker O-Ring Handbook ORD 5700, sections 3.5 to 3.7 (stretch, squeeze, gland fill), and Table 8-4 (NAS1613), read 2026-09-24
- Parker compound E3609-70 datasheet (FDA), read 2026-08-13
- Parker ethylene propylene 70 durometer O-ring datasheet (drinking water and medical), read 2026-08-13
- 21 CFR 177.2600
- AMS7259
- AMS7276
- AS3208
- AS3209
- AS568
- AS83248
- ASTM D1418
- MIL-P-82744
- NAS1613
- NSF/ANSI 51
- NSF/ANSI 61
- USP Class VI
Frequently asked questions
Can I use Viton for steam?
No: the Parker handbook rates FKM unsatisfactory in steam and names an EPDM compound (E0692-75) for it; EPDM steam grades reach 204 C. Where the same system also sees oil, FFKM rates satisfactory in steam in the same table.
Can EPDM take any oil?
Silicone oils and greases, yes. Petroleum and mineral oils, no.
Which one for glycol-water coolant?
EPDM, unless the system also sees engine oil, in which case FKM or HNBR.
Which one lasts longer outdoors?
Both resist ozone and weather; EPDM does it at lower cost where no oil is present.
Which one for ketones like acetone?
EPDM. Ketones swell FKM heavily. For mixed aggressive streams, FFKM (see the guide FFKM vs Fluorocarbon (FKM) O-Rings in the guides section).
Which fluids does Parker's E3609-70 EPDM datasheet list?
Start with the exclusion: mineral oil products, meaning oils, greases and fuels, which is fluorocarbon's home ground. What the sheet lists sits on the water and polar side: glycol-based brake fluid and phosphate-ester hydraulic fluid, hot water and steam, polar solvents, many acids and alkalis, and silicone oil and grease, with ozone and weather resistance on top.
Is there an aerospace EPDM specification?
Yes: NAS1613, the phosphate-ester resistant O-ring document. Parker's handbook pairs its E0515-80 with Revision 2 and E1267-80 with Revision 5 (Table 8-4). Fluorocarbon has no place in that fluid, which is a clear example of the media deciding the material.
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