Is there a drain plug on your 1996 Chevy blazer to out old gas?

No, there is no drain plug on a 1996 Chevy Blazer's fuel tank to drain old gasoline. Fuel tanks are sealed units. To remove old gasoline, you would need to siphon it out using a siphon pump or other appropriate method. Be extremely careful when doing this, as gasoline is highly flammable and its vapors are explosive. Never attempt this near an open flame or spark. Proper ventilation is also crucial.