ShelfYears

Does WD-40 expire?

Not in any way you will notice — WD-40 Company says the product performs as expected for an almost indefinite period, and the 5-year figure it publishes is a rating for the can's valve, not for the liquid inside it.

Updated

WD-40 & penetrating oil
Sealed
5+ years
Opened
Same 5+ years
VALVE & PROPELLANT LOSS
Harmless

Sealed: 5+ years Tier 1

WD-40's own FAQ answer: the product "should continue to perform as expected for an almost indefinite period of time," but because actual performance depends on mechanical parts like the valve assembly, "the shelf life is considered to be 5 years from the date of production; however, product will often dispense and perform as expected for considerably longer." That is a can rating with a fluid that outlives it.

After opening: Same 5+ years Tier 1

An aerosol has no opened state the way a bottle does — the valve is the seal, and it stays shut between sprays. Nothing about the first use starts a new clock. What shortens the window is heat: WD-40's safety data sheet asks for a cool, well-ventilated spot and says the can should not be stored above 120°F or in direct sunlight.

How to tell it's gone off

  • A can that spits, dribbles or hisses in ordinary use instead of throwing an even fan.
  • The can still feels heavy but nothing sprays — the propellant has escaped and the liquid is stranded inside.
  • A blocked nozzle or a lost straw is the usual culprit; a fresh straw often revives a can that seemed dead.
  • Rust or corrosion around the rim, seam or base of the can, which is a container problem rather than a contents problem.

If you use it anyway

Harmless

Old WD-40 is a non-event. The maker's own words are that it "should continue to perform as expected for an almost indefinite period of time," and its safety data sheet calls the formula not reactive under normal conditions — the published 5-year number describes the valve, not the oil. The worst outcome a careful reader should plan for is a can that will not spray, which costs a walk back to the shelf and nothing else.

Why it goes off — VALVE & PROPELLANT LOSS

The liquid is a stable petroleum blend — WD-40's safety data sheet calls it not reactive under normal conditions, and there is no gum, no separation and no additive package to spend. The aging happens to the package: propellant works its way past the valve seal a molecule at a time, the valve stem can crust with dried carrier, and a hot shelf speeds both up. Old WD-40 fails by not coming out, never by coming out wrong.

Every page here commits to one of four states — Harmless · Degraded performance · Equipment damage · Safety issue. How the verdicts work.

How to store it

WD-40's FAQ sets the band: store the can between 4°C and 54°C (39°F to 129°F) and shake it before use. Its safety data sheet is stricter about heat and is the one to follow in a garage — a cool, well-ventilated place, away from oxidizers, never above 120°F and never in direct sunlight.

Sources