we're not talking about plain old por-15. i'm talking about the gas tank treatment that is made for the inside of the tank. i've painted the outside of the tank with regular por15 but have used the gas tank treatment for the inside. now i'm trying to figure out what to do with all the leftover gas tank treatment i have left. BTW. i think regular por is great stuff for rust preventative. i've just finished a total undercoat.