Quote Originally Posted by kings1527 View Post
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.
http://www.sterlitech.com/oring-compatibility-chart


I see viton listed all over the map for both gasoline and ethanol.

One thing I see that's consistent is Buna-N for both gasoline and ethanol resistance. It is *the* recommended material for both. Who is manufacturing your o-rings? Are you sure you're getting what you're paying for?

Just an FYI, I have extensive experience in the vacuum technology and industrial chemistry world and deal with chemical compatibility for these types of seals for both terrestrial and space applications. What I think is that you guys are picking up 3rd rate o-rings and are making assumptions. The available data out there from the manufacturers and industry publications suggest that Buna-N is the stuff you want for o-rings for cars. They've been using ethanol in gasoline since the 1920s (granted, the o-ring didn't exist in the 1920s) and is not new.

There are plenty of reasons to go with viton, but I don't think I know of any where it comes to dealing with cars.

-Bob