It’s wise to make every effort you can to cover up exposed wires before cleaning your engine. It might not seem like a big deal, but getting a chemical cleaner or too much water into a cracked or frayed wire can cause it to short circuit and potentially result in expensive repairs. It’s also a good idea to cover up any opening in the intake system. If your engine has a carburetor, try not to let the engine degreaser or too much water get inside. Check the label on the specific product you’re using. If it says that it’s not safe for tires, then cover up your tires. If it says to avoid getting it on your exterior paint, then do what you can to cover the areas of the car that could be exposed to the degreaser. If you’re nervous about harming other parts of your car, then it’s a safe choice to go with one of the water-based degreasers that are safe to use on pretty much any surface, but you’ll still want to read the directions on the label.