The friction will decrease on applying oil on door hinges because:

⇒ When oil is applied between the moving part of a door, a thin layer is formed there.

⇒ Due to which the moving surfaces do not directly rub against each other.

⇒ As a result, friction reduces and the movement of door becomes smooth.

Note: The substances which reduce friction are called lubricants. For example – oil, grease, graphite etc.