A clean engine compartment makes a used car look newer and better maintained. Some shops that perform engine cleaning services claim a clean engine even runs a little cooler because removing the gunk formed by dirt, oil and grease allows engines to run cooler.
Appearances aside, does a clean car engine that sparkles like new run any better than one that’s grimy from normal use? Do you absolutely need to remove the debris or use a degreaser to keep your car in proper working order? Probably not.
Though it is true that while oily, greasy dirt that accumulates on an engine can trap some heat, it’s doubtful it would be enough to cause an engine to overheat or even run hotter than normal. If a car engine overheats, the probable cause is more likely in the cooling system — or because the car is towing or carrying too much weight, or some other issue unrelated to the cleanliness of the engine bay. There is no evidence to suggest that a cleaner engine runs better than one that is dirty. It is unlikely that something as simple as a little decreaser or cleaning spray could make a vehicle run better.
A Cleaner Engine Does Offer Some Benefits
However, cleaning your car engine does offer certain benefits. First, doing so helps determine where oil or grease is coming from — such as a leaky valve-cover gasket — so that a small problem like a minor oil leak can be isolated and repaired before it becomes a big one. In addition, because oil and grease can accelerate the wear of rubber hoses and plastic parts, using degreaser to clean off the gunk may save on repairs. And if you’re the type who likes to do some minor maintenance, such as checking the oil level or accessory belts, a clean engine means your hands and clothes are less likely to get dirty.
Many mechanics and detail shops recommend using a degreaser and tools such as a vacuum with a small nozzle, compressed air or a toothbrush to get at hard-to-reach spots. Those are preferable to blasting an engine with a high-pressure hose or steam cleaning an engine, because water and moisture can damage electrical connections and parts. Even a slight spray of water in the wrong place could cause serious problems. Engine detailing requires precision and a gentle touch; trying to tackle this project at the car wash or with water from your garden hose could spell disaster.
The cosmetic appeal of a clean engine will probably be the biggest payback. Most used cars are thoroughly detailed before being put up for sale, including many sold by private owners, so buyers have come to expect to see a clean engine when they shop. A dirty engine on a used car will hurt its curb appeal.