That thought never occured to me...
Do you feel you need one to prevent someone from putting some foreign material into the tank to cause you harm?
Then again, I did not look. Maybe you have a big tractor with a large fuel tank. /forums/images/graemlins/smile.gif
Mine only holds 5 or 6 gallons. The locking cap would cost probably three times what the tank of fuel costs.
Now that you got me thinking, maybe I better start taking the keys out of my tractors... /forums/images/graemlins/blush.gif