If someone steals a couple of gallons of gas, your 10$ cap has paid for itself. Also, you might need that full tank some morning when you rush out...only to realize the neighbor kids took about half your tank the night before. It's also dangerous to have someone siphoning gas out of your tank. STANT makes good caps, and most auto supply stores will have a locking cap for your car. You do NOT have to buy one at the dealer.
