Quote Originally Posted by rdarlington View Post
Actually from what I'm reading, Viton is actually a poor choice for ethanol. It's marginal at best.

Simply put, if Buna-N o-rings are deteriorating because of modern fuels, it is most definitely NOT because of the ethanol in them.

-Bob
Not sure where you're reading about Viton being a poor choice for ethanol but that's not right. It's not so much a matter of deterioration, but rather swelling resulting in deformity. That's why the PPR o-ring starts having problems. It becomes malformed and can't hold rest pressure. I've personally (as have others) seen a nice swollen buna-n o-ring from ethanol based fuel.

In short, go with Viton unless you want to look cool working on your car all the time.

And a special thanks to Dave M for all of his research and info on this.