Yes, one type is head and shoulders better than anything else we can put in for gasoline. For inside the tank, Viton is the best and is also 10x the cost. I am using 60 durometer which is soft. The 75 durometer is fine for outside the tank but a bit stiff for inside

For outside the tank, I use Nitrile, but you can't go wrong with Viton there too. I have also used neoprene (LHS will carry this material)but didn't care for it. It cracked in only a couple months. Nitrile, neoprene, and the many varieties of Tygon, all will need replacement annually, and neoprene more often than that. Viton will not need replacement for many years.

Point is that you have few options....the best type will set you back around 3.5-4$ per foot.

BTW- I am also experimenting with PUR to find how this material will work. All this stuff will eventually find its way into our cookbook recipe