Quick Answer
CSM offers a strong balance of weather, ozone, chemical durability and process economics; FKM is a premium choice for high temperature and aggressive fuel/chemical sealing. They often serve different performance tiers.
CSM vs FKM: practical comparison
| Selection factor | CSM | FKM |
|---|---|---|
| High-temperature capability | Moderate/high specialty range; grade/compound dependent | Generally superior |
| Fuel/chemical resistance | Broad but not universal | Very broad, especially hydrocarbons |
| Weather/ozone | Excellent | Excellent |
| Cost | Lower specialty tier | Premium |
| Typical role | Outdoor/chemical rubber, hose covers, cable | High-performance seals, fuel systems, hot chemicals |
How to choose
Use FKM where high-temperature and severe fluid resistance are non-negotiable. Use CSM where outdoor/chemical durability and component economics are more important.
Important: Ratings describe general polymer-family tendencies. Exact performance can change materially with grade, formulation, cure system, fluid composition, temperature and test method.
Frequently asked questions
That framing is too broad. They have different strength areas and must be compared against the actual service conditions.
Both can perform well; the full compound and other requirements decide the choice.