Heavy keychains harm ignition lock cylinders. They result in excessive wear and might lead to premature failure. Carlos went on to add that the following automobile manufacturers are particularly vulnerable to tumbler or ignition problems caused by hefty keychains: Ford, Honda, Hyundai, Kia, Mazda, Nissan, Pontiac, Subaru. If you notice any strange sounds when turning the key in the ignition, this could be a sign that you should switch off your keyring. Swapping out keys that are making noise for new ones will help prevent future problems with your engine. Keys can also be a cause of concern if they're not working as expected. If you need to use another person's car but they won't let you because their key doesn't work on your vehicle, this could be due to excessive wear and tear on their part. Have them drop their key ring so you can give their keys a make over from the spare key hole!