The number of cars a professional detailer can wash in a day varies widely based on several factors, including the type of detailing services offered, the size and condition of the vehicles, and the specific detailing methods used.

1. Basic Car Washes: In a typical car wash setting, a detailer might handle 6 to 12 cars per day if they focus on quick exterior washes or basic cleaning services.

2. Full Detailing Services: For more comprehensive detailing tasks, such as interior cleaning, waxing, or paint correction, the number of cars detailed can drop significantly. A professional might only detail 2 to 4 cars per day, as these jobs require more time and meticulous attention.

3. Factors Influencing Capacity: The time it takes to detail a car can depend on its size, level of dirtiness, and whether it requires specialized treatments. Larger vehicles and those needing extensive cleaning will naturally take longer​.

In conclusion, while a detailer might wash a higher volume of vehicles when focusing on quick services, more thorough detailing typically results in a lower daily count.