I haven't tried this yet, but I have used ammonia to clean oven shelves by pouring some in a heavy duty garbage bag and leaving the shelves in there to soak before scraping them with a steel wool pad.
Using ammonia seems a great way to clean the oven:
Preheat the oven to 150
degrees F. While the oven is heating, put on a pot of water to boil. Once the
oven has reached 150 F, turn it off and pour 1 cup of ammonia into a heat safe
bowl or baking dish and place it on the top rack of the oven. Place the pot of
boiling water on the bottom rack, close the oven door, and leave them both in
the oven overnight.
The next morning,
open the oven and remove both the bowl of ammonia and the pot of water. Don’t
dispose of the ammonia; you’ll want to use it later. Remove the racks and leave
the oven door open to air out for 15 minutes. Add 1-2 teaspoons of liquid dish
soap to the ammonia, along with a quart of warm water, and using a heavy-duty
nylon scrubbing pad dipped in the ammonia mixture, begin to wipe away the
softened grease and grime along the sides and bottom of the oven. It should be
a fairly easy job at this point. Wear some kitchen gloves, since ammonia can be
caustic to skin. However, I found it interesting that the ammonia was WAY LESS
powerful smelling after having sat overnight in the oven. Rinse/Wipe Clean with
a damp cloth.