When storing gas for mowers, etc., should a plastic gas can be sealed or allowed to vent? With E0, I normally loosen the collar to allow venting. However, with E10, I'm not sure that's a good idea, as it promotes water absorption. I believe it's safer to vent, but better for the E10 to seal. If this is just short-term storage of E10 (say, a month), is it fine just to vent the can?