In the long run you'll be better off getting a new "jug". Check your local salvage yard for used replacements. A new replacement (not OEM) from car-stuff.com will run about $200. What has happened is the UV protection coating has eroded away, and the underlying polycarbonate is being damaged by sunlight. The snake oil sold in the store will only last for a few months, and you'll be back in the same situation.