A quick spray is not the same as a lasting lubricant
A hinge squeaks when its moving surfaces rub against each other. WD-40 Multi-Use Product can quiet that friction at first: its solvent helps the liquid creep into the hinge’s narrow gaps, while its water-displacing action can push moisture away from the metal. That can be useful if dampness is contributing to the noise.
But the spray is designed primarily to penetrate and displace water, not to leave behind a durable lubricating layer. Its volatile ingredients evaporate, and the residue left behind is too thin to protect a hinge through repeated movement for long. The squeak may return as the surfaces rub together again.
What a hinge needs instead
For ongoing lubrication, use a product intended to remain between moving parts, such as a light machine oil or an appropriate grease. Apply a small amount where the hinge knuckles meet, then move the door back and forth so the lubricant works into the joint. Wipe away excess to limit drips and dust buildup.
If the hinge is dirty or rusty, cleaning it first can help; adding lubricant over grit may leave the joint messy without solving the source of the noise. WD-40 can be a temporary aid, but a lubricant that stays in the hinge is what keeps the fix from being temporary.
