Robertof

Went out and checked under the truck for the drain hole and there is a drain, but it has a quarter inch hose connected to it, that goes back to the tank. I still think a slip over cap is the way to go. Don't know if its true, but the dealer said it has the smaller second trap door to keep dummies from filling the tank with diesel !

I have a 2017 Silverado Z71. I found that the cap from a can of Krylon paint fits perfectly and just a little snug on the capless fuel filler, and its FREE. When looking for a spray can cap, be sure it fits inside of the rim of the can , some caps fit over the rim and will be too loose