Can you damage a car by washing it too often?

Keeping a car clean seems to be a good thing for several reasons, but is it possible to wash a car too much, to the extent of causing damage to the paint or anything else? SB

How “often” does not matter.  How “gently” does.

Modern cars are extremely weatherproof. They can get rained on every day and come to no harm at all. “Gentle” washing mimics that, with plenty of clean water and a soft cloth. Nothing else.

Harsh or clumsy washing can do damage primarily through abrasion – the dirt being cleaned off works like sandpaper if the water is scant or the material used to wipe is rough.

Where higher water pressures are used, a degree of moderation and common sense is necessary, to avoid forcing water into places not designed to get wet or stay wet or using a pressure jet so powerful that it causes physical damage. 

Bear in mind that the No 1 jet in a pressure washer can deliver a lance of water with, at very close range (a couple of inches), enough force to chop a brick in half! The power decreases rapidly with increasing distance, but it can still cause injury.

Gentle washing with clean water does not immediately remove a protective coat of wax polish. Soap or other detergents should not be used frequently on the paintwork. They can be used more often on tyres and rubber floor mats, tougher and powder-coated wheel rims.

Polish itself often contains a mild rubbing compound, and should be used only occasionally, to help restore faded or stained paintwork; only the paint, nothing else.

The interiors of cars are not weatherproof and include a lot of fabric, which does not thrive on water or harsh rubbing. When they do need attention, vacuuming is the best first step (to remove abrasive grit without touching it), followed by a branded upholstery foam and gentle damp sponging. If the car’s use is likely to get the seats and panels really dirty, washable seat covers are the best solution. 

Hard plastics can be more regularly and conventionally washed, and if that is done correctly, they are unlikely to get deep dirt or stains. If they do, occasional scrubbing and detergents are unlikely to do them harm.

Engine compartments do not contain primary painted surfaces (so no problem on that score), but they do have components (usually electrical, and especially the alternator and ignition items) sensitive to water so circumspection and mechanical knowledge are necessary ingredients.  

Soap and scrubbing of the non-sensitive hardware (the engine itself is waterproof) are fine, and if the dirt is oily rather than muddy, a pre-wash using petrol applied with a paintbrush can be helpful.

It can be advisable to wash the engine compartment when it is warm, so water accidentally splashed onto sensitive items or trapped in nooks and crannies, self-dries quickly. Start the engine as soon as possible after washing to assist that process.

The underside of the floorpan obviously has to be very weatherproof, so vigorous spraying with a garden hosepipe is safe, and even high-pressure washers can be used...with some “aiming” sensitivity when they are pointed at soft rubber grease boots.

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