Locked gas caps become more popular when gas prices rise, or people worry about vandalism in their communities. The problem with locked gas caps is you should have a key to open them. Just like car keys, house keys and bike lock keys, gas cap keys can easily be misplaced or forgotten. But when you have the key, removing your locked gas cap to fill your tank should be easy. You may need to manoeuvre the key in a certain way, so make sure to read the manual or try it out before you are on empty. For example, with Stant Locking Fuel Caps, you must make a 1/4-turn of the key to open any of their locks. For older gas caps, you may need to wiggle the key in the hole a little first or make sure the cap is tight before the key can fit in the slot and unlock the cap.
Use a screwdriver
If you don't have a key, you can use a flathead screwdriver to remove the locked fuel cap. First pry off the key hole cover with the screwdriver, then pry the lock mechanism out and remove the cap. If the cap locks internally and doesn't have a keyhole, you should be able to force it open by inserting the screwdriver into the side of the cap and springing the release mechanism.
Remove the lock
Another method that will remove the cap is to drill a 0.5 cm hole through the outer part of the fuel cap and insert a sharp, pointed drywall screw into the lock. When you feel resistance, you should have locked the two halves together, so you can then screw off the entire cap.
Call a locksmith
If you want to keep the lock in one piece without destroying it or prying it open, then you may need to find a locksmith. A locksmith can usually pick the lock just as he would if you locked your keys in your vehicle.