The hinges on an oven door heat up when the oven is in use. Over the years the factory applied lubricant or oil gradually wears off the hinges. When this happens the hinges begin to squeak. The squeaking is caused by the metal parts of the hinges rubbing together when the door is opened and closed. Applying a general purpose grease or high-temperature oil to the hinge stops the squeaks and won't melt away when heated.
Turn the oven off. Allow it to cool.
Grip the oven door handle and pull it open.
Apply general purpose grease or high-temperature oil to the pivoting joints of the hinges. Application methods vary depending on the design of the grease or oil container. Squirt or spray the grease or oil and then wipe off the excess with a rag.
Open and close the oven door several times until the squeaking stops. The lubricant will work its way into the hinge as the door is opened and closed.