Renowned mechanic Scotty Kilmer has issued a strong warning to car owners: washing your engine bay with water and cleaning agents can seriously damage your vehicle. Scotty explains that the engine compartment houses sensitive electronics and computer modules that are vulnerable to water exposure.
“Cleaning your engine with any type of cleaner followed by hosing it down is a bad idea,” Scotty said. “Water and cleaners don’t mix with the delicate electronics under the hood. Over the years, I’ve seen many cars brought in with check engine lights on, only to find damage caused by power washing under the engine.”
He advises drivers to reconsider the necessity of cleaning engine bays altogether. “Do you eat on your car’s engine? Do you constantly look at it? A little grease can actually protect against rust and doesn’t harm anything. If you want to keep your car clean, focus on the parts you see all the time—the exterior and interior surfaces.”
While proper car washing is important, the RAC recommends a more cautious approach. They suggest using a pressure washer or, at minimum, a garden hose with a spray gun, along with two buckets, car shampoo, a wash mitt, and microfiber drying towels. For best results, wash your car in the shade and ensure no rain is expected, as rapidly drying shampoo can leave streaks.
Ultimately, when it comes to the engine bay, less is more. Avoid spraying water directly onto sensitive components and protect your car’s vital electrics by leaving engine cleaning to the professionals or limiting it to dry methods only.