I found out about Viton seals and o-ring a long time ago, but in a different application...Hot water flow guages. For some reason, the guy in the job before me was always looking to save $1...or any portion thereof.
So he bought a huge quantity of "Buna-N" rings. System had 6 flow guages, requiring a full overnight period to change out rings in 1 guage. By them time I got guage 6 re-ringed, guage 1 was streaming water out like the open end of a fire hose. (lather, rinse, repeat)
After buying the Viton rings and installing them in all 6 gauges, it was 2-1/2 years before any guage started leaking.