A degreaser is a cleaner that can remove grease and oils from engine parts. It can help you avoid lots of scrubbing if you need to clean a dirty part. Aerosol degreasers can reach small crevices easily. You can also immerse a dirty part in a water-based degreaser. Using a degreaser can help you prevent corrosion and keep components working well. Some degreasers are flammable, and others contain potentially toxic chemicals. Only use a degreaser when your car's engine is cool, and make sure there's plenty of ventilation in the area. Some degreasers can damage plastic or rubber seals, or gaskets. Test any new degreasers before you use them extensively.