Review on Gates 31778 Locking Fuel Tank Cap: Secure Your Fuel with Advanced Locking Technology by Charles Salgado

Used on 1999 Dodge. Don't bother. You need to use the key to lock it and make sure it is screwed all the way onto the gas filler neck. You can attach it without a key, but sealing the tank won't do the trick. If you have a petrol engine, it will likely set the evaporator code. My truck is diesel so that's not a problem for me. I also have a gas cap with a lock and it works much better. Closes without a key and screws tight. This also works with our toy truck so you know where it went. This cap does lock in and keep thieves out, but I think it's too heavy to use. I would keep looking.