OK then Les, how about the fact that all cars have a pressure/vacuum regulating gas cap to prevent air pollution. For those of you who care about the environment, (I don't have kids and live in New Jersey), it seems that if the gas is oxidizing and evaporating, it isn't getting any fresher. I think I will plan to cap one of the vents, (the side with the barbeque grill), except while filling, any harm in that?