Being the impatient guy i am, I called Sullivan. He wasn't sure, and said that it varies by fuel additive by state. He said 2 years ago they had to reformulate their stoppers because of additive changes. Thye tested fine everywhere except California and Hawaii. He is going to email me with what the tech guys say, but I'm still going to test it for myself. It's kind of scary knowing that what may be gas proof one year, is not the next.[]