Wipe oil from inside the microwave with paper towels.
Place a microwave-safe bowl filled with white vinegar or a 50/50 mixture of water and lemon juice inside the microwave oven.
Set the microwave on high, and cook the liquid for 10 minutes. The mixture will begin to produce steam, which will loosen greasy residue and eliminate odors from the fire.
Leave the bowl in the microwave for 15 minutes. Moisten a clean sponge in the mixture. Scrub inside the microwave with the sponge to remove residue from the oil fire.
Rinse the inside of the microwave with a damp cloth, and dry it with a towel.
Moisten a clean sponge in pure white vinegar, and use it to clean the outside of the microwave. Rinse the sponge in water as necessary, add more vinegar, and continue cleaning.