Always use gasoline stabilizer fluid if you store gasoline for more than a few weeks. Gasoline is hydrogoscopic and leeches water out of the air even inside a sealed container. Also it, when in a stored state, forms a kind of waxy material . That's why your weed-eater won't start after you stored it over the winter without draining the fuel and blowing out the carburetor. Gasoline with ethanol is the worst for storage. Never store it, even in your automobile if the car sits for a few weeks without running.