Car Cleaning – Foam Party at the Car Wash

In spring, it’s time for a thorough car wash. This requires the right care products, cleaning equipment, and a good washing area. However, it’s not a good idea to tackle the paintwork using household remedies. We asked DEKRA expert Thilo Kunst how to successfully spring clean a car.

In spring, many car owners take great pleasure in giving their car an extensive hand wash and rinsing the traces of winter from paint and rims. However, cleaning the car requires some preparation. First and foremost, this includes a suitable washing area. After all, it’s not only biodegradable cleaning agents that mix into the wash water, but also oil and soot particles that have no place in groundwater. The washing station of a self-service car wash is therefore the best choice, because these facilities work with filters and special separators. In addition, the right cleaning and care products are needed to ensure that the foam party is a brilliant success. So do you just add a dash of washing-up liquid to lukewarm water and rub the paint vigorously? That wouldn’t be a good idea, explains DEKRA expert Thilo Kunst from the DEKRA Laboratory for Environmental and Product Analysis.

Using home remedies for hand washing attacks plastic and paint

“With most home remedies, you don’t know the material compatibility. Unsuitable cleaners can cause paints, plastics, or rubbers to swell, discolor metals, or lead to stress cracks in the polycarbonate of headlights,” explains the expert in automotive chemistry. Material compatibility is therefore one of the most important laboratory tests for products such as windshield and rim cleaners, car shampoos, and insect removers on the testing schedule. It’s often manufacturers, suppliers, and dealers who require an assessment by the accredited DEKRA laboratory before placing a cleaning agent on the sales shelf. The chemical and physical tests for material compatibility take place under precisely defined laboratory conditions at temperatures of up to 80 degrees Celsius. The testing plan also includes performance tests with thoroughly dirty vehicles. Here, DEKRA experts also use a sponge and brush to assess cleaning performance. Thilo Kunst hasn’t yet come across an all-purpose cleaner that could clean paint, windows, and rims equally well. For a simple reason, as the expert reports: “The formulations of the cleaning agents are tailored to their specific purpose. A windshield cleaner is the right agent for windshields, a rim cleaner for rims.”

Insect remains on the window are a case for a special cleaner

Thilo Kunst pays particular attention to windshield cleaners that are filled into the car’s washer tank. In this product class, new agents come onto the market every year – windshield cleaners are therefore among the most frequently tested automotive chemistry products in the DEKRA laboratory. “As the months get warmer, the dirt cocktail on the windscreens changes. In spring, motorists should therefore switch to a summer windshield cleaner for the frost-free period,” recommends Thilo Kunst. These cleaners are designed to effectively tackle summer dirt, which is high in protein. A winter cleaner, on the other hand, doesn’t have this special talent. The DEKRA expert advises against continuing to use the winter agent in summer. This results in insect residue being removed less well and dirt on the windscreen easily smearing. However, even summer windshield cleaners often have problems with dried insect residue on the windshield. In this case, an insect remover is an effective resource. These agents often have a gel-like consistency that adheres perfectly to dirt residue. After a short exposure time, the residue can then be removed with a sponge and water.

Rim cleaners make short work of brake dust and dirt

One of the particularly difficult places to clean are the rims. Frequent braking and a high rotation speed of the wheels can cause brake dust and road dirt to bond firmly with the rim’s metal. This dirt can often only be removed with the assistance of a rim cleaner. A typical substance in these agents is sodium captoacetate, which has an excellent cleaning effect on metal and brake abrasion. A rim cleaner’s chemical feat ultimately consists in the fact that, on the one hand, it powerfully tackles dirt, but at the same time doesn’t impair the paint, plastics, and rubbers in the area of wheel carriers and chassis parts. Alkaline and acidic rim cleaners with high or low pH values have comparatively short exposure times. Due to their aggressiveness towards metals, these products are often only allowed to remain on the rim for up to one minute before they have to be rinsed off thoroughly with clear water. PH-neutral products are less critical for the material and can also be kept on the rim for five minutes or longer.

Car shampoo and polish provide brilliant results

Most car shampoos are excellent specialists when it comes to cleanliness. Their surfactants are usually perfectly adjusted to the dirt typical of road traffic and enable good foaming. When buying, anyone expecting a particularly good cleaning result should look out for the DEKRA seal, which documents precisely this property. However, it’s a fallacy that lots of car shampoo in the cleaning bucket also helps a lot. Thilo Kunst advises to always pay attention to the manufacturer’s instructions for use and contact time when using cleaning and care products. After washing the car, new paintwork will usually look new. Those who value a high-gloss result can also use a paint preservative. These products are free of abrasives and contain water-repellent components such as waxes and silicones. They also seal and protect the paint surface against external influences. If the paint on older cars appears dull and matt, a paint cleaner may be the solution. It smoothes the paint by abrading a very thin layer of paint. A preservative then provides a water-repellent protective layer in the second step. In lighter cases, a polish can also be a good choice. It combines the properties of paint cleaner and preserver, but contains significantly less abrasive substances.

This is how the car wash succeeds at the wash station

DEKRA expert Thilo Kunst recommends a thorough prewash with clear water. This removes dirt particles, sand, and small stones, especially in the vehicle’s lower area. The cleaning itself should take place from top to bottom. Start with the roof and work your way down the sides to the door sills. The sponge should frequently be washed out well so that no dirt particles scratch the paintwork. The car is rinsed off with clean water. If you want to avoid unsightly water spots on the paint, wipe the car dry with a clean chamois leather or microfiber cloth.


  • Cleaning utensils such as high-pressure cleaners can be found in most self-service boxes. Be careful with the equipped brushes – check condition carefully before use
  • Your own equipment should include a sponge, wash glove, wash brush – all in clean condition?
  • Use two buckets – one for care products, one with clear water for rinsing the tools used
  • Change water often during washing
  • Dry cloth, leather cloth, microfiber cloths
  • Care and cleaning products


  • Pre-cleaning avoids paint damage due to dirt and sand particles
  • Spray off surface dirt, sand, and road salt with plenty of water
  • Pay attention to underbody and door entrances
  • Keep a distance of around 40 centimeters with a high-pressure cleaner

Wheels and rims

  • Basic cleaning with high pressure cleaner
  • Finish with a sponge and shampoo
  • A rim cleaner helps against stubborn dirt – follow the manufacturer’s instructions for use and application time


  • Insect remover helps with dried insect residue and other dirt
  • Fold up windshield wiper, clean rubber lips
  • Apply car shampoo or glass cleaner, wipe in circles with microfiber cloth
  • For clean windows, it’s recommended to clean the inside with glass cleaner


  • Use lukewarm water and car shampoo for cleaning
  • Shampoo the paintwork only with gentle pressure from a sponge or wash glove
  • Watch out for dirt on door frames and hinges
  • Rinse the car body from top to bottom with clear water. High-pressure cleaners usually have their own program for this purpose
  • Dry the paintwork with chamois leather or microfiber cloth to avoid water spots

Plastic strips and door rubbers

  • Refresh colors of plastic trim with care product
  • Protect door rubbers from drying out with rubber care product

Paint cleaning and preservation

  • Treat dull and matt paint surfaces with paint cleaner
  • Use paint preservative for the care of intact and new paintwork. Paint preservative is also appropriate for paintwork that has been pre-cleaned with paint cleaner
  • In light cases, use polish
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