Yesterday when it rained and snowed and then froze, I could not unlock my driver's side door with the key. The key wouldn't go all the way in (if you know what i mean)...

I wound up unlocking the doors from the passenger door lock, then crossed my fingers and gave the driver's door handle a tug. It worked. Once i warmed the car up, i could unlock/lock the driver's door.

SO. my question is, 1. how can i prevent this in the future? 2. I'm tempted to spray graphite into the lock, but don't want to cause more problems till i get your guys feedback.

Thanks in advance.

I keep a can of WD40 with me for this reason. They make small "mini cans" that work well. Its probably not the best solution, but it works. I spray the locks once a month during winter.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car