WD-40 in the Stockpile: What It Is Good for, What It Is Not, and How Long a Can Lasts

Freeing rusted bolts, nuts and hinges; driving water out of a wet ignition, a flooded outboard, a soaked flashlight or radio; stopping flash rust on tools and steel after they get wet; cleaning grease, sap, tar, adhesive and crayon; loosening a stuck zipper or a frozen padlock long enough to get it open. It is the can you reach for when something is seized, wet or gummed. It is not the can for keeping something lubricated.

The WD-40 Company puts the shelf life at 5 years from the production date printed on the can, and cans routinely work well past that. What fails first is the propellant: an old can hisses and dribbles instead of spraying. The liquid inside is still good, so a dead can gets punctured outdoors and decanted into a squeeze bottle. Kept cool and out of the sun, expect ten years of usable product from most cans.

Cool, dry, dark, upright and under 120°F. It is a pressurized, flammable aerosol, so it does not live in a hot attic, a sealed shed in summer, a vehicle, or near a stove, water heater or torch. A cabinet in the house or a shaded outbuilding is right. Keep the little red straw taped to the can; it is the part you lose.

It is a petroleum solvent. Breathing a lot of the mist irritates the nose and lungs, it dries and irritates skin with repeated contact, it stings the eyes, and swallowed it can get into the lungs and cause chemical pneumonia, which is why nobody should be made to vomit after drinking it. Used outdoors or in a ventilated shop with the can pointed away from your face, it is an ordinary shop chemical. Keep it off skin you eat with and out of anything that holds drinking water.

Yes, on damp tinder. A short burst on a cotton ball, a pine cone or a bundle of shavings lights with a spark and burns hot enough to dry the kindling around it. It is a starter, not a fuel: it flares, drips and is gone in a minute or two, so never build a torch or a lamp with it, never spray it at an existing flame, and keep the can well away from the fire once it is lit.

Several small cans. An 8 oz can goes in the truck, the go-bag, the generator box and the tool bag, each one a fresh propellant charge. One big can with the straw stays in the shop for everyday use. A gallon jug with a trigger sprayer is the cheapest way to own the liquid if you use a lot of it, and it does not depend on propellant at all.

Only briefly. It leaves a very thin film that helps a squeak for a few days, then evaporates and leaves the surface dry with dust stuck to it. For anything that keeps moving, wipe the WD-40 off and use the right thing: grease on hinges and bearings, oil on a chain, dry graphite or PTFE in a lock, gun oil on a gun. WD-40 is the cleaner and water displacer you use first.

Locks (it gums them; use graphite or dry lube), bicycle and chainsaw chains (it strips the real lubricant), firearm actions as a lubricant (fine as a cleaner, wiped off, then gun oil), rubber seals and gaskets over time, clear polycarbonate and polystyrene plastics, anything that touches food or drinking water, and electrical contacts that are live. It also dissolves the wax off gear you waxed.