How to clean an engine?

Foreword

Like anything else, engines work better when they're clean. But cleaning an engine is not the same as cleaning the rest of your car. With the right procedure, you can keep your engine in tip-top shape. No need to hire a professional; you won't need anything you can't find lying around the house.

Find the good degreasing product

Degreasing products come in two types: solvent and water-based. Both types work on greasy engines. And both require special environmental handling once they’re applied—even if the label says “environmentally safe” or “biodegradable.” Because once the degreasing solution starts dissolving the grease, it’s considered hazardous waste.

We prefer solvent-based degreasers because they work faster and seem to cut through heavy grease buildup better than most water-based products. The downside is their strong solvent smell. If you’re sensitive to solvents, choose a concentrated water-based product instead.

To get better “cling” on vertical surfaces, choose either foam or a gel formula.

Methods to clean your engine

Degreasers work best when the grease is warm and soft. So start the engine and let it run for about five minutes. Then shut it off and let it cool down until you can safely touch the exhaust manifold. Never spray cleaners (especially flammable solvent types) on a hot engine.
 
If you’re using a concentrated water-based product, test it on a greasy spot. If it doesn’t cut the grease fast enough, add more concentrated degreaser to the brew.
Next, seal all the electrical connections. Then set the absorbent mats under the engine to soak up the runoff. Prep the worst areas. Then apply the degreaser. Aim carefully to prevent the overspray from reaching painted areas. Rinse lightly with water and remove the plastic wrap. When you’re done, place the wet mats in sunlight to allow the water to evaporate. Then dispose of the mats following local regulations.
 
For extra protection, spray an engine protectant.