I have had the same cap on my fuel jug since the late '90s. Plug your fill line onto the vent & the fuel will stay good. I hauled a partial gallon of 15% Cool Power W/the cap & fuel lines set up like that out of a closet that had set for 14 years right next to an unopened jug. i strained it through a coffee filter to filter out some fine white particles & tried it on my test stand. It ran just as good a the unopened jug which performed the same as some brand new 15% Cool Power I bought @ the LHS.