As others have said, dry graphite is what is generally recommended as lock lube. I use it by blowing it into the lock with a small tube-applicator, run the key in and out and turn it a few times, then take compressed air and blow into the lock to blow out any excess graphite. That seems to work well for me. Just remember to wipe the key off before you put it in your pocket or you will have black stains from it on your hand, pants and anything else you touch!

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz