When should you grease a door hinge? When it's dry or when it starts making noise? Is there a universally appropriate type of grease to use? How should it be applied?
I would grease the door hinges once or twice a year. When it comes to grease, having too much is never a bad thing other than the fact that it makes a mess.
The best type of grease to use is white lithium grease because it is thick and will not run out of the door hinge.
To apply it just spray it in the gaps between the door part of the hinge and the body part of the hinge and open and close the door to work the grease into the hinge.
Ideally you want to grease before it squeeks.If you wait until it is squeeking you have metal on metal contact somewhere in the hinge.That kind of contact results in hinge wear.As a side note an unlubricated hinge requires more effort to close the door and that can resultin broken armrests or door pulls.I generally lube the drivers door every other oil change and the other doors,hood and trunk once a year.