Spray-can engine cleaners are a cheap and common method of cleaning engines that washes away with water. However, because it is dangerous to get certain parts of the engine wet, water-free spray can solvents, also known as carb cleaners and brake cleaners, can erase grease and oil easily but are far more expensive. Many professional shops use steam cleaners, which are powerful and thorough but can damage the engine.
For small and greasy spots, the spray can solvents work best. Larger engine cleaning projects can be done with the spray can engine cleaners, provided care is taken to avoid getting moisture on the wire connectors or the secondary ignition system.
Although not suggested for every car, steam cleaning has been shown to increase engine life and lower the risk of engine fires. However, the high-pressure steam can often cause wiring to disconnect or expose the ignition system to water, damaging it considerably and requiring expensive repairs.
Keeping an engine clean helps mechanics and car owners to find fluid leaks and worn belts. Regular cleanings also prevent rust from forming and increase the resale value in the future. A major concern with do-it-yourself engine cleanings is pollution; the water runoff is loaded with grease and oil that damages the environment.