I have been using O-rings made of Buna-nitrile (Buna-N) from Ace Hardware in my (ZS) carbs and they have not leaked or otherwise failed. Just my experience, should not be taken as Gospel. Geo On Tue, May 7, 2013 at 9:00 AM, <fogbro1 at comcast.net> wrote: > What is the recommended for 'O' rings exposed to fuels with ethanol > content?