Can I use WD-40 in a Frozen Car Lock?

No! Don’t ever use WD-40 in your car locks. WD-40, and similar petroleum based lubricants can, over time dry into a sticky film that not only inhibits the moving parts inside the lock but also traps the dirt and road grime leading to all sorts of lock failure. If you need to lubricate your auto locks, use a Teflon or silicon based lube. These are found in most hardware and home improvement stores.