What should I use to lubricate a lock, and why not WD-40?
Which lubricant belongs on a cylinder, a mechanism, a hinge and a rubber seal — and why the aerosol most people reach for is the wrong answer for exactly one of them.
- Difficulty
- beginner
- Time
- 10 min
- Read
- 4 min
Short answer
Cylinders: a PTFE-based lock lubricant or powdered graphite, nothing oily. Mechanisms, bolts and hinges: light machine oil or a silicone spray. Rubber seals: a silicone rubber conditioner, never oil. Tracks and runners: dry PTFE, because oil turns grit into grinding paste.
Nearly all door and window hardware asks for one of four things, and the reason a general-purpose water-displacing aerosol has a bad reputation is narrower than the internet suggests. It is a poor lubricant for a pin cylinder specifically, because it flushes out the existing lubricant and leaves a residue that attracts dust into the pin chambers. On a hinge or a bolt it is unremarkable rather than harmful — just not as good as oil.
Step by step
- Match the lubricant to the mechanism, not to the door.A single door may need three different products: graphite or PTFE in the cylinder, oil in the multipoint mechanism, silicone conditioner on the gasket. Using one product everywhere is how a well-meaning annual service does harm.
- Use PTFE or graphite in any pin cylinder.Euro cylinders, rim cylinders, padlocks and window locks all use small spring-loaded pins in narrow chambers. They need a dry or near-dry lubricant that will not hold dust. A puff of graphite or a short burst of a PTFE lock spray, then the key worked in and out a dozen times.
- Use light machine oil on mechanisms and bolts.Multipoint drive rods, hooks, rollers, mortice lock cases through the forend, nightlatch cases, espagnolette gearboxes, friction stays. Three-in-one type oil or a sewing machine oil is exactly right. A drop, not a flood.
- Use oil or silicone on hinges.A drop at the top of the barrel and work the door. Silicone spray is cleaner and does not run down a white frame; oil lasts longer. Either is fine.
- Use a silicone conditioner on rubber seals.EPDM gaskets swell and soften when oil is left on them, and a swollen gasket makes a door stiff and then perishes early. A silicone rubber conditioner keeps them flexible.
- Use dry PTFE on sliding tracks.Patio door tracks, bifold guides and sliding wardrobe runners. Oil or grease in a track collects grit and turns into a grinding paste that wears the rollers out. Clean the track first, then a dry PTFE spray.
- Clean before you lubricate.Every product works better on a clean part, and lubricating over grit simply distributes it. Wipe bolts, tracks and hinge barrels first.
- Apply little and often rather than a lot once.A lock does not need soaking. Excess oil runs down the door face, marks the frame, and picks up dust that ends up back in the mechanism.
- Never use grease in a cylinder.Thick grease in a pin cylinder stops the pins returning in cold weather, which produces exactly the winter key failure people are trying to prevent.
Common mistakes
- One aerosol for the whole house — The products do genuinely different jobs. The cheapest possible set of three covers everything and costs less than one call-out.
- Lubricating a lock instead of fixing what is stiff — Lubricant masks a misaligned door for a few weeks. The bolt is still bearing on the keep, and the gearbox is still taking the load.
- Oiling a rubber gasket to stop it squeaking — It swells the rubber, which makes the door stiffer and eventually destroys the seal. Silicone conditioner does the same job without the damage.
Alternatives
- PTFE lock spray: The default for cylinders. Dry film, does not attract dust, works down to low temperatures. Widely sold as 'lock lubricant'.
- Powdered graphite: The traditional cylinder lubricant, sold in a small puffer tube. Extremely effective and long-lasting, but it is black and it will mark a light-coloured door if you are careless.
- Light machine oil: The right choice for lock mechanisms, hinges and bolts. Cheap, available everywhere, and the thing to reach for on anything that is not a cylinder or a rubber seal.
- Silicone spray: Good on hinges, seals and plastic-on-plastic contact. Clean and non-staining. Not a substitute for oil inside a heavily loaded mechanism.
Questions people ask
Is WD-40 actually bad for locks?
For a pin cylinder, yes in practice: it displaces the existing lubricant and leaves a thin residue that holds dust in the pin chambers, so the lock is better for a fortnight and worse within a year. On hinges and bolts it is simply unexceptional rather than damaging. The same manufacturer sells a specific PTFE lock product, which tells you something.
How often should I lubricate?
Once a year for everything, done as part of an autumn service. A door in a coastal or very exposed position benefits from twice.
My lock squeaks. Is that a warning?
Usually just dryness. But if it is stiff as well as noisy, treat the stiffness as the real signal and check the door alignment before reaching for a can.