Auto antifreeze is lethal to animals and fish, local dog or cat licks up your puddle, dead, not so hot for the lake/river when you launch either. Plus pink is a 1/4 the cost. The other possible concern is glycol (car) antifreeze dries down to a real sticky shit, not sure I'd want that in my exhaust, pumps etc drying out through the winter, pink is alcohol based and dries out to pretty much nothing.