Your lock is stiff. You reach for the WD-40. Spray, work the key in and out, and it feels better. Problem solved?
Not quite. You’ve just made things worse—and in a few months, that lock will be stiffer than before.
The WD-40 Misconception
What WD-40 Actually Is
The name reveals the truth: Water Displacement, 40th formula. It was developed to:
- Displace moisture (rust prevention)
- Loosen seized parts temporarily
- Clean surfaces
- Provide very short-term lubrication (enough to work a freed component)
It excels at these tasks. It is not, and was never intended to be, a long-term lubricant for precision mechanisms.
Why It Seems to Work Initially
When you spray WD-40 into a stiff lock:
- The solvents dissolve existing grime
- The petroleum distillates provide momentary slipperiness
- The mechanism moves freely again
This feels like success. But:
- The solvent evaporates within hours to days
- The remaining residue is sticky, not slippery
- Dust begins accumulating
- Weeks later, the lock is stiffer than before
"WD-40 on a lock is a maintenance debt. You borrow short-term improvement against long-term degradation.
What Actually Happens Inside Your Lock
Lock Mechanics 101
Inside your cylinder:
- Pins of various heights respond to key cuts
- Springs push pins into position
- The plug rotates when pins align correctly
- Tight tolerances mean even small debris matters
For smooth operation:
- Pins must move freely in their chambers
- Springs must compress and release cleanly
- Surfaces must slide without friction or catching
WD-40’s Effect
After application and evaporation:
- Dusty residue coats pin chambers
- Springs contact sticky surfaces
- Fine grit binds in the remaining film
- Precision tolerances are compromised by debris
Over multiple applications, this buildup compounds. Each spray adds more residue that never fully leaves.
What to Use Instead
Graphite Powder
The classic lock lubricant—used by locksmiths for decades.
Advantages:
- Dry lubricant—doesn’t attract dust
- Long-lasting protection
- Extremely low friction
- Won’t gum up over time
How to use:
- Puff small amounts into keyhole
- Work key in and out to distribute
- Wipe excess from key and lock face
- Repeat annually - see our complete lock maintenance guide
Disadvantages:
- Messy (grey-black powder)
- Can stain hands and clothes
- Needs application directly into mechanism
PTFE-Based Lock Lubricant
Modern alternative to graphite, often in spray form.
Advantages:
- Similar dry-lubrication properties
- Generally cleaner to apply than graphite
- Long-lasting
- Often available in precision applicators
How to use:
- Apply per product instructions
- Usually a small spray into the keyhole
- Work key to distribute
- Wipe excess
Disadvantages:
- More expensive than graphite
- Quality varies between brands
Silicone Spray
Another option, though with caveats.
Advantages:
- Clean application
- Broadly available
- Works on many mechanisms
Disadvantages:
- Some formulations attract dust (check for “dry” silicone)
- Often applied too heavily
- Less effective than graphite for locks specifically
Maintenance Schedule
Annual Lock Care
Once a year (perhaps when clocks change as a reminder):
- Blow out loose debris from keyhole
- Apply small amount of graphite or PTFE lubricant
- Work key in and out several times
- Wipe key clean
- Test operation
Seasonal Adjustments
- Before winter: Lubricate to prevent cold-weather stiffness
- After prolonged dampness: Check for moisture, lubricate if lock feels rough
- After construction/renovation: Clear dust contamination
Reactive Maintenance
If the lock becomes stiff:
- First, try proper lubrication
- If no improvement, the lock may need professional cleaning
- Repeated issues suggest replacement consideration
What If You’ve Already Used WD-40?
Single Use
Probably fine. The residue from one application is minimal. Apply proper lubricant on your next maintenance cycle.
Repeated Use Over Time
If you’ve been using WD-40 for years:
- The lock may have significant residue buildup
- Professional cleaning can sometimes restore function
- Replacement may be advisable if performance is poor
- Don’t add more WD-40 trying to fix it
Other Lock Care Tips
Key Maintenance
- Keep keys clean
- Replace worn keys promptly
- Don’t use keys as tools
- Store on rings that don’t bend them
Lock Environment
- Protect exterior locks from direct rain where possible
- Check for moisture ingress after storms
- Ensure weatherproofing is intact
Professional Servicing
- Annual check from a locksmith catches developing issues
- Particularly valuable for high-security locks
- Less expensive than emergency calls when locks fail
Frequently Asked Questions
Can I use WD-40 on my locks?
No. WD-40 is a water-displacing solvent, not a lubricant. It may help briefly but then evaporates, leaving residue that attracts dust and worsens the problem over time.
What should I use to lubricate locks?
Use graphite powder or purpose-made lock lubricant. These are dry lubricants that don't attract dust or leave residue. Apply annually or when stiffness develops.
Why do people think WD-40 works on locks?
WD-40 does provide temporary improvement by flushing debris and displacing moisture. This creates the illusion of success. The long-term damage becomes apparent weeks or months later.
How often should I lubricate my locks?
Annual lubrication with graphite or lock-specific lubricant is sufficient for most locks. Locks exposed to weather or heavy use may benefit from twice-yearly treatment.
Is WD-40 ever appropriate for locks?
Only in an emergency to free a completely seized lock—as a one-time measure followed by proper lubrication and potentially professional cleaning. Not for routine maintenance.
My lock is still stiff after proper lubrication—what now?
Internal damage, debris the lubricant can't reach, or worn components may be the cause. Professional assessment is warranted.
How much lubricant should I use on locks?
Less than you think. A small puff of graphite or brief spray is sufficient. Excess makes mess without adding benefit.
Can I use cooking spray or motor oil on locks?
No. These are not designed for lock mechanisms and generally cause more problems than WD-40.
Take Action
If there’s WD-40 next to your locks “for maintenance,” it’s time for a change:
- Purchase graphite powder or proper lock lubricant
- Apply to all external locks
- Work keys to distribute
- Throw away or relocate the WD-40 (it’s useful for other things)
- Add lock lubrication to your annual home maintenance routine
Your locks will work better, last longer, and you’ll avoid the slowly-building problems that WD-40 creates.