My bathroom door squeaked so loud it woke up my partner every time I got up at night. I grabbed the WD-40, sprayed the hinge, and it was quiet — for about three days. Then it came back louder. WD-40 is not a lubricant. It is a water displacer. It cleans gunk out of the hinge and then evaporates, leaving the metal parts grinding against each other again.

What actually lubricates a hinge

You need something that sticks around. The best options you probably already own:

• Petroleum jelly (Vaseline). Thick, waterproof, and it does not drip. The best choice for most door hinges. It fills the microscopic gaps between the hinge pin and the knuckles and stays put for years.
• Bar soap. Works surprisingly well. Rub a dry bar of soap directly on the hinge pin. The wax and fats provide enough lubrication to stop squeaking, though it does not last as long as petroleum jelly.
• Cooking oil. Works in a pinch — olive oil, vegetable oil, whatever is in the kitchen. It will quiet the hinge for weeks to months. Downside: it can drip onto the door frame and go rancid eventually.
• Silicone spray. If you want to buy something, silicone spray is the correct product. It is a dry lubricant that does not attract dust.

How to do it properly

1. Open the door partway. Place a wedge or folded towel under the door so it does not move.
2. Tap the hinge pin up and out. Use a nail and hammer — place the nail tip against the bottom of the pin and tap upward. Once the pin is partly out, grab it and pull.
3. Coat the pin with petroleum jelly. Not a huge glob — a thin layer all the way around.
4. Wipe the inside of the hinge knuckles with a paper towel to remove any old gunk or metal dust.
5. Slide the pin back in. Tap it down gently with the hammer until it is seated.
6. Open and close the door a few times to distribute the lubricant. Wipe away any excess that squeezes out.

My bathroom door has been silent for eight months. I did all three hinges in the apartment in about twenty minutes. The one hinge where I used bar soap is still quiet too, though I suspect I will need to redo it before the petroleum jelly hinges need attention.