bradleyban

I use Buna-n or Viton for inside my gas tanks. It's a little bit pricey but it will not go hard with time and being submerged in fuel or oil won't affect it like tygon will. I use Tygon on all exterior parts of the tank and the Buna on all the interior.

One thing about buna and Viton is you need to use barbs on the brass tubes at the stopper