Karcher notes that vehicles that are dirty inside or out offer a poor first impression to customers.
It advises that when treating the inner surface of windows, cleaning agents that turn to gel upon contact with the glazing are ideal. They do not run off the glass.
It also says that microfibre cloths with a 16x fold should be used to remove dirt, as they do not transport it further.
Wet and dry vacuum cleaners are suited to flooring, while spray extraction machines can be used on carpets and seats to remove dirt. Karcher advises treating seats thus once or twice per year and that the vehicle is aired well afterwards.
When cleaning the exterior, Karcher says that before starting, rim cleaners and insect removers should be applied to radiators and the windscreen – but not in direct sunlight, as they will dry faster, inhibiting their effectiveness.
Hot water cleaning machines are more efficient, it continues. The higher temperature enhances performance and better dissolves greases and oils. Karcher also advises that for large vehicles such as coaches, a foam cleaning agent should be applied beforehand.