Almost everyone reaches for the same can when a lock stops turning: WD-40, straight into the keyhole. And almost everyone is half right. A penetrant is exactly what a gritty, stiff lock needs in the moment — but it is not a lubricant, and sprayed in and forgotten, it sets the lock up to seize again, often worse, within a season.
The fix that actually lasts is a two-step process, and the second step is the one nearly nobody does.
This guide covers the whole picture: the two-minute fix for a lock that won't turn or a key that won't seat right now, why locks stiffen up in the first place, the lubricant that's actually correct for a lock cylinder, why the obvious go-to product is only half the answer, and how all of this plays out differently on an exterior deadbolt, an old furniture lock, a padlock, and a lock that's frozen solid.
⚡ Quick answer
If a lock won't turn or the key won't seat, spray a penetrant into the keyway (not the faceplate, not a padlock's shackle) to clean and free it, work the key gently, then once it's moving, follow up with graphite powder or a PTFE-based dry lubricant for the lasting fix.
Never use oil, grease, or petroleum jelly as a long-term lock lubricant — all three attract the dust and grit that jam pins.
| Right now | Penetrant into the keyway, work the key gently, don't force it. |
| For good | Graphite powder or PTFE dry lubricant, puffed or sprayed into the keyway once it's clean and dry. |
| Never | Oil, white lithium or any grease, petroleum jelly — all trap grit inside the mechanism over time. |
01 · THE TWO-MINUTE FIX
The lock won't turn right now — do this first
If you're standing at a door that won't unlock, here's the sequence, in order.
- Don't force the key. A key that's fighting hard against a jammed cylinder is a key one hard twist away from snapping off inside the lock — a far worse problem than a stiff lock. Back off the moment you feel real resistance.
- Spray penetrant into the keyway, not around it. The mechanism is inside the cylinder. A spray around the faceplate or the surrounding metal does nothing for the pins; it has to go into the actual keyhole. A thin straw nozzle helps aim it.
- Work the key gently. Insert and withdraw it several times without forcing a full turn, letting the penetrant work its way across the pin stack. Try turning with light, steady pressure rather than a hard twist.
- Try the key at slightly different depths and angles. Sometimes a lock only binds at one point in its rotation; a slight wiggle while turning frees it.
- If it's a deadbolt and knob together, try each independently — a stiff knob and a stiff bolt have different causes and don't always fail at the same time.
That gets most stuck locks moving again. But a penetrant is a cleaning product, not a lubricant, and this is exactly where most people stop and unknowingly set themselves up to be back here in a few months.
02 · WHY LOCKS STIFFEN UP
Why locks stop turning smoothly
A lock cylinder is a set of spring-loaded pins that has to move freely every single time, with no lubrication schedule and no attention from anyone — until it doesn't work. Four things cause almost every stiff lock.
- Old lubricant has dried out or turned gummy. Oil left in a cylinder for years oxidizes into a sticky varnish that grabs the pins instead of freeing them.
- Dust and grit are bound into old wet lubricant. This is the real case against oil and grease in a lock: they don't just lubricate, they collect every particle that drifts into the keyway and hold it right where the pins move.
- Rust on the pins or the bolt, especially on exterior locks that see rain and humidity, or on old hardware that's sat unused.
- A misaligned strike plate or a sagging door, which is not a lubrication problem at all — the bolt is fighting the frame, not the cylinder. If a lock feels stiff only when the door is closed, and easy when it's open, this is almost always the cause, and no amount of lubricant fixes it. A carpenter's adjustment or a re-set strike plate is the actual repair.
03 · THE RIGHT LUBRICANT
Graphite vs PTFE: the two lubricants that actually belong in a lock
A lock cylinder wants a dry lubricant — something that reduces friction without ever being wet enough to hold dust. That rules out almost everything people instinctively reach for, and leaves two genuinely correct choices.
| Lubricant | How it works | Trade-off |
|---|---|---|
| Graphite powder | Microscopic slick particles that coat the pins and slide past each other; nothing to dry out or gum up. | Cheap, simple, the traditional standard — but it's a black powder that can blacken a light-colored key or your fingers if you overdo it. |
| PTFE (Teflon) dry lubricant spray | A carrier solvent flashes off and leaves a dry PTFE film behind — same dry-lubrication principle as graphite, delivered as a spray. | Cleaner and easier to aim precisely into a tight modern cylinder; slightly pricier than a tin of graphite. |
Either is correct. Graphite is the traditional, dirt-cheap standard that's been the right answer for decades; PTFE spray is the modern, tidier equivalent that's easier to control. What matters is staying dry.
⚠ What never belongs in a lock
Oil, white lithium grease, any other grease, and petroleum jelly all share the same flaw in a lock: they're wet, and wet lubricant holds dust and grit right at the point where the pins need to move freely. Every one of them turns a smooth lock into a gritty one over a season or two, even though each one feels like it's helping on day one.
04 · WHERE WD-40 FITS
Is WD-40 bad for locks? Where penetrants actually fit
WD-40, CRC, and 3-IN-ONE aren't wrong for a lock — they're incomplete. As penetrants, they're genuinely excellent at exactly what a jammed lock needs first: displacing moisture, dissolving old gummed-up lubricant, and flushing grit out of the pin stack. That's the right emergency move, and it's why it's step one in this guide too.
The trouble is what happens next. These products are solvent-forward by design — that's what lets them penetrate so well — and the light oil film they leave behind evaporates over weeks, not years. Left as the only treatment, a penetrant-only lock dries out again and returns to square one, and the solvent can even strip away whatever old lubricant was still doing some good: penetrants are the shower, not the lotion. They clean beautifully. They don't moisturize.
So the honest sequence is: penetrant to clean and free the lock, let it dry fully, then graphite or PTFE to actually lubricate it for the long run. Skipping straight to a dry lubricant on a gritty, gummed-up lock just traps the grit under a fresh coat; skipping the follow-up dry lubricant leaves the lock to seize again once the solvent evaporates. Both halves matter. For the fuller case on why a penetrant alone isn't a lubricant, see when to use original WD-40 around the home, and for the same principle applied to hinges and gates, the best oils to lubricate an exterior gate.
05 · HOW TO APPLY IT
How to lubricate a lock properly
Aim into the keyway, every time. Whatever you're applying — penetrant or dry lubricant — it only helps if it reaches the pins inside the cylinder. Spraying the brass faceplate around the hole does nothing.
Using graphite powder: puff a small amount directly into the keyway, then insert and work the key back and forth several times to spread it across the pin stack. Wipe the key itself afterward so it doesn't blacken pockets, bags, or hands.
Using PTFE spray: a short burst straight into the keyway is usually enough. Work the key the same way, then wipe any excess from the faceplate.
One thing that trips people up: on a deadbolt, spraying into the throw-bolt hole in the door edge does nothing for the key cylinder — they're separate mechanisms. Lubricate the keyway for the cylinder and, separately, a light touch of dry lubricant on the bolt itself if it's dragging against the strike plate.
06 · BY LOCK TYPE
Interior, exterior, old, new, and padlocks — what changes
Interior doorknobs and passage locks
These rarely see weather, so the usual culprit is years of accumulated dust rather than rust. A light PTFE spray or a small puff of graphite is generally all an interior lock needs, and it's often years between treatments.
Exterior deadbolts and entry locks
These face rain, temperature swings, and airborne grit, so both the cylinder and the moving bolt need attention. Follow the full sequence — penetrant, then graphite or PTFE — and check the strike plate and latch for wear at the same time, since exterior hardware takes far more cycles per year than an interior door. If rust has actually taken hold on the bolt or visible hardware, deal with that directly: see how to stop rust coming back after you remove it.
Old and antique locks (furniture, cabinets, old doors)
Old skeleton-key and warded locks usually have a different problem than a modern cylinder: decades of dried oil and caked-in old graphite, sometimes literally solid inside the mechanism. Lubricant isn't the first move here — gentle mechanical cleaning is. Compressed air and a soft brush to loosen and clear old debris, worked patiently, before any new lubricant goes anywhere near it. Only once it's genuinely clean does a fresh, light application of graphite make sense. On brass or aged finishes, test any modern spray product on a hidden spot first — some solvents can dull old plating or lacquer.
New or unusually stiff locks
A brand-new cylinder that feels tight is often just manufacturing tolerance on a fresh, gritless pin stack — not a fault. A light settling-in dose of graphite or PTFE, worked in with normal use over the first week or two, is usually all it takes; there's rarely anything to clean out first.
Padlocks
A padlock has two separate things that need attention, and treating them the same is the most common mistake. The keyway and internal mechanism want the same dry lubricant as any other lock — graphite or PTFE, never grease. The shackle pivot is a completely different job: a bare metal hinge point exposed to weather, which benefits from a light coat of oil or grease for corrosion protection, the same way any exterior hinge does. Lubricating the mechanism and protecting the shackle are not the same task, even though they're one padlock.
07 · FROZEN LOCKS
Frozen locks and freeze-thaw seizing
Cold-weather lockouts have a different cause than everyday stiffness: moisture that got into the cylinder freezes solid, or ice forms directly around the pins, and the key simply can't move anything until that ice is gone.
- Warm the key, not the lock. Heat a metal key briefly with a lighter or a match, then insert it — the warmth transfers into the immediate ice around the pins without you needing to touch an open flame to the door itself. Repeat a few times as needed.
- A hand warmer or warm (not hot) water bottle held against the cylinder works the same way, more slowly and more safely for finished hardware.
- A dedicated lock de-icer or lock antifreeze spray is built for exactly this and is worth keeping in a car or by an exterior door in freezing climates.
- Don't pour boiling water on a lock (it can warp or crack finishes and refreeze into new ice moments later), and don't force the key against solid ice — that's how keys snap.
Once it's thawed and turning, don't stop there: dry the cylinder out and follow the same penetrant-then-dry-lubricant sequence from earlier in this guide. A lock that froze once with moisture inside it will do it again next winter unless that moisture and any resulting grit gets properly cleaned out and replaced with a dry lubricant that won't hold water against the pins.
08 · PREVENTION
Keeping it from happening again
Locks are one of the few mechanisms in a house that get zero scheduled maintenance until they fail. A little prevention is genuinely cheap insurance.
- Once or twice a year, or at the very first sign of stiffness — not after it's fully seized — give exterior locks a light dose of graphite or PTFE.
- Keep exterior keyways covered where practical (a keyway cover or storm-door position that shields the lock from direct rain) to slow how much moisture and grit gets in to begin with.
- The single habit that prevents most of this guide from ever being needed: apply dry lubricant before a lock seizes, not after. A lock that's never been neglected rarely needs the emergency penetrant step at all.
Frequently asked questions
Can I use WD-40 in a lock?
As an emergency step, yes — it's excellent at cleaning grit and freeing a stiff lock. As a long-term lubricant, no; it evaporates within weeks and can strip away lubricant that was still working. Follow it with graphite or a PTFE dry lubricant for a lasting fix.
What is the best lubricant for a door lock?
Graphite powder or a PTFE (Teflon) dry lubricant spray. Both stay dry inside the cylinder, so they lubricate the pins without attracting the dust and grit that jam a lock over time.
Why is my key hard to turn?
Usually dried-out old lubricant, dust and grit trapped in old oil, rust on the pins, or a misaligned strike plate putting mechanical strain on the bolt rather than the cylinder. The first three respond to cleaning and dry lubricant; the last needs an adjustment, not lubricant.
Why won't my key go all the way into the lock?
Debris or a buildup of old, gummed lubricant inside the keyway is the most common cause. A penetrant spray followed by gently working the key in and out usually clears it; if the key still won't seat, don't force it, since that's how keys snap off inside a cylinder.
How do I fix a frozen lock?
Warm the key with a lighter and insert it repeatedly, use a hand warmer against the cylinder, or use a dedicated lock de-icer spray. Avoid boiling water and never force the key against ice. Once it's thawed, dry it out and lubricate it properly so it doesn't refreeze the same way next time.
Can I use oil or grease in a lock?
It's best avoided. Oil, white lithium grease, and petroleum jelly are all wet lubricants that trap dust and grit inside the mechanism, which is exactly what makes a lock stiff and gritty over time. Use a dry lubricant instead.
How often should I lubricate a lock?
Once or twice a year for exterior locks, or as soon as you notice any stiffness. Locks get no scheduled maintenance otherwise, so a light annual dose of graphite or PTFE prevents most emergency call-outs to this guide in the first place.
My old lock is gritty and black inside — what do I do?
That's usually decades of old oil or graphite caked together, common in antique furniture and door locks. Clean it out gently first with compressed air and a soft brush rather than adding more lubricant on top, then apply a light fresh dose of graphite once it's genuinely clean.
The bottom line
A stuck lock has a two-step answer, and almost everyone only does step one. Penetrant cleans and frees a gritty lock brilliantly, but it evaporates and leaves nothing behind — that's a cleaning product, not a lubricant. Graphite or PTFE dry lubricant is the part that actually keeps a lock turning smoothly for the next year, because it stays dry and never collects the dust that jams the pins in the first place. Do both, keep grease and oil out of the keyway entirely, and treat a padlock's shackle and its lock mechanism as two different jobs. Do that, and the next stuck lock in the house is a much rarer event.
For the penetrant step in more depth, see when to use original WD-40 around the home; for the same wet-vs-dry lubricant logic applied to hinges and gates, the best oils to lubricate an exterior gate; for why grease specifically doesn't belong in a lock, what makes white lithium grease the right lubricant for metal parts; and if rust is part of the picture on exterior hardware, how to stop rust coming back after you remove it.
