I have the Carb ones already for months now and they dont leak a drop, even from getting hot and cold as long as you have the metal cap on tight. the thing that sucks about the carb cans is they come with this sub standard plastic spout that does not seat well so it dribbles out the side as you try to pour and also the spout is some sort of spring mechanism that requres you to insert a small funnel into your tank then line up the spout and then press down to start the fuel to flow. the non carbs just have a simple bendy hose that goes right into the fuel tank and has no flow restrictor. I have not filled the non carb ones yet but from the design being so simaler I have confidence that they will not leak. I will post up results when I fill em, probably not til gas drops down under 355 a gallon.