I was worried about some scumbag thug pouring fluids that don't belong in my diesel or diesel exhaust fluid, so i went to ACE & bought a lock kit with 2 keys for $6.95. I removed the fuel door & drilled the fuel door from the inside of the door with an 11/16 drill bit, make sure you place the fuel door on top of a piece of wood with a rag under the fuel door, once lock was installed i had to grind the tab so it lock. Now i don't have to worry.