** Warning **
A lengthy read but worth it if you use a cheap car wash.
The cheap roadside or supermarket car wash is likely doing your car more harm than good.
They are cheap and convenient so the temptation to use them as a regular way to keep your car clean is hard to resist and for under £10 it all sounds great so why wouldn’t you use them?
Here are some reasons worth considering…
The first thing your car is normally subjected to is an application of diluted traffic film remover (TFR) via a pump sprayer and this is bad in two ways. The first is that this strong chemical is very good at removing grime but will also strip any wax or protection your paintwork already has. This leaves it exposed to day to day wear and the elements. If you paid for a nice Lifeshine treatment or have a ceramic coating then this could damage or completely remove it. A second concern is that TFR should be applied to a pre-rinsed (i.e. wet) car. If applied to a dry surface there will be a risk of damage to the top layer of paint (clear coat). The severity is dictated by the strength of the dilution. Along with this there is also the possibility of damage to chrome, plastic and rubber trim.
They are also known to use some rather unorthodox methods whilst washing your car!
Wheels are often treated with the same TFR or an acid based product normally via a pump sprayer. The acid products give quick results but are very aggressive. Both can cause damage. Your vehicles wheels will inevitably be hot due to heat soak from the brakes and calipers. This causes the water in the solution to evaporate quickly allowing the chemical to dry or begin to dry on the finish. Using these products on warm or (worse) hot wheels, will generally result in some form of damage to the wheel and caliper finish.
The small buckets of water you see the staff working with at supermarkets are far too small to have sufficient water to adequately clean a go-kart never mind a car. At other washes the large tank they have will be a soup of grit and grime from other cars. The sponge or rag they are using is the same one that was used to clean the filthy 4×4 that was before your vehicle. If you want your car washed with dirt this is definitely a great way to achieve it.
The correct shampoo is important. It should be ph neutral to ensure no damage is caused to any existing protection on the paint and should also provide good lubricity. The latter helps to remove the dirt from the paint efficiently with minimal micro scratching. Cheap shampoos will not provide these requirements and cannot be provided within the budget restraints of a £5 wash.
Washing cars with the traditional sponge has been identified as one of the biggest causes of damage to vehicle paint. Sponges trap dirt between the surface of the paint and the 
surface of the sponge. This creates a mild sandpapering effect leading to the fine scratches, surface hazing and swirl marks that are easily seen on almost all vehicles in bright sunlight.
Understanding the correct way to clean a vehicle may sound ridiculous but there really is a right and wrong way to do it. Employing the correct technique will minimize micro scratching and swirl marks, ensure all areas are effectively cleaned and reduce the risk of other common problems arising like premature drying of shampoo that causes staining/streaks etc. Along with these factors it is also worth noting that cleaning a car should be done carefully and should not be time restricted in any way. A standard safe maintenance wash can take at least an hour, often longer, and not the 5 mins these people take regardless of how many staff they have.
Drying the vehicle is the next pitfall and damage can occur by the use of incorrect methods and equipment. The biggest problem is the use of rubber drying blades. These will drag any remaining tiny pieces of dirt or grit across the paint leaving scratches that can sometimes be deep and difficult to remove even with machine polishing. Even after a car has been cleaned the chances of there still being some small particles of dirt or grit on some of the panels is extremely high. Chamois leathers tend to have a similar problem to sponges with regards to trapping grit and then dragging it around. When you also consider that they are rarely rinsed out and normally just wrung out the probability of being contaminated with dirt is high. The safest way to dry a car is by blown air. If that is not available then a good quality microfibre drying towel.
Silicone based dressings used on bumpers, plastic and rubber trim and tyres have a sticky consistency that attracts dirt/dust and can leave a patchy finish. It has a tendency to look unnaturally shiny and whilst this can be instantly gratifying the result is short lived and has a tendency to eventually turn brownish in appearance.
Waxes and polishes used at such car washes are again heavily silicone based, offer little actual protection or durability and are generally not what you want on your vehicles paint. They are often being applied and removed with unclean or contaminated cloths and rags which can also add fine scratches to your vehicles paint. The minimal benefits of these cheap products are far outweighed by the potential problems that can arise. If you are going to have wax applied to your car then it should be as clean as possible beforehand including tar removal, industrial fallout removal and use of a clay bar. This simply cannot be done in the time scales offered by cheap car washes. They are simply applying wax over a whole load of collected grime.
Another reason to avoid these car washes is from an environmental stand point. (This will not apply to legitimate, legal car washes that capture their waste water or use bio degradable products.) Employing the use of cheap chemicals will normally mean using non bio degradable, environmentally harmful products that if washed into drains can end up in rivers and waterways. They can be problematic to ecosystems and wildlife.
In addition to all the above there is also a very real concern about some car washes being involved in modern day slavery. This cannot apply to all but there is evidence to show that, like nail bars and other similar establishments, car washes are a way of forcing people into labour. When you consider the fly by night nature of some of them it is easy to conclude that products are cheap and staff are poorly paid if at all.
Many car owners are unaware of the potential problems that can arise from a cheap washes and the costs involved in rectifying them. If you do care about your vehicle, these reasons are definitely worth considering as is the employment of a professional. The quality of service offered between a ten minute car wash and a professional safe clean is immeasurable. The old saying that you get what you pay for was never more true.
My advice, if you love your car and want to protect your investment, is to employ a professional to look after it.
An article below from GEM Motoring Assist covers many of the same concerns.
https://blog.motoringassist.com/…/cheap-car-cleaning-that-…/
The Clewer Initiative from the Church of England is helping to identify modern day slavery car washes with its Safe Wash scheme
