What about FKM (Fluorocarbon) O-Rings?

FKM, also known as Fluorocarbon or Viton® is a brand of synthetic rubber and fluoropolymer elastomer. Standard durometers are 75 and 90 and they typically come in black or brown.  The temperature range is generally -15-degrees to 400-degrees.  FKM is available in standard and metric sizes.

FKM has good resistance to petroleum products and a wide spectrum of chemical compatibilities. Recommended uses include vacuums, most acids and chemicals, halogenated hydrocarbons, di-ester lubricants, petroleum oils and fuels, silicone oils and greases.  FKM has excellent resistance to high temperatures, ozone, oxygen, mineral oil, synthetic hydraulic fluids, fuels, aromatics and many organic solvents and chemicals.

FKM is not recommended for hot water and steam, and also has problems with ketones, auto and aircraft brake fluids, amine (ammonia), acetone, skydrol, ethyl acetate, and low molecular esters and ethers.

FKM is not recommended for low temperature uses and for static applications is limited to approximately -15-degrees although in certain situations it is suitable down to -40-degrees. Under dynamic conditions the lowest service temperature is between 5 to 0-degrees.

FKM has good wear resistance, excellent compression set resistance, moderate short-term resilience and excellent permeation resistance. It is good for vacuum service and low gas permeability.