I’m often asked if it’s “OK” to spray WD-40 into a lock or into a keyhole or keyway. The answer is ABSOLUTELY YES! There are many misconceptions about WD-40 that have been around for years, one of the biggest is that WD-40 contains water, this is not true, and in fact WD-40 displaces water when sprayed onto metal surfaces. The W -stands for water and the D -stands for displacement. Another big misconception is that 
WD-40 gums up a lock over time if sprayed into the lock, this simply is not true. I have been using WD-40 to lubricate locks for over 30 years and I can tell you emphatically that “WD-40 DOES NOT gum up locks”. WD-40 is a light lubricant and degreaser. It’s true that it’s lubricating ability won’t last as long as something like 3-in-1 oil, but check this out —> 3-in-1 oil sprayed into a lock WILL eventually become rather sticky and thick and cause the lock pins to move up and down sluggishly, I know because over the past 30 years I have tried 3-in1 and WD-40 when lubricating locks. WD-40 will not get gunky / sticky the way 3-in-1 will. In particular I like to use WD-40 for spraying into the keyway where you insert the key. Because it is a light lubricate and tends to evaporate over time, you use it more often, but, because it’s a thin lubricant it’s less likely to attract dirt and works great for “washing out dirt and debris from the keyway, also great for squeaky hinges. If you choose to use graphite (which I detest because it’s messy) you might want to try the “white” graphite instead of the “black”, the black graphite will get on your hands and clothes when you touch the key after pulling it out of the lock. WD-40 is your friend, don’t be afraid to use it. 🙂
WD-40 Myths:
- WD-40 contains water (Not True)
- WD-40 gums up locks (Not True) -In fact it’s a degreaser so it dissolves gum / great for removing adhesive from labels too.
WD-40 Facts:
- WD-40 is a great light lubricant for locks.
- Often if your key is hard to push into the lock, spraying some WD-40 into the keyway will allow the key to push into the lock.
- WD-40 works wonders for squeaky hinges and linkages, just spray directly onto the affected area.