Detailing a ton of cars and over the years, I have developed a method of determining how dirty an interior of a car. How I determine how dirty a car is is by how many bottles of cleaner we go through to cleaning a car. Normally most cars use a 1/2 to a full bottle of cleaner and a large SUV uses 1 to 1 1/2 bottles of cleaner. The dirtiest car I have ever done used 16 bottles of cleaner. The dirtiest car this year is 7 bottles.