The number of cars you can effectively clay bar with a single clay bar depends on several factors, including the size of the clay bar, the size of the cars, and the level of contamination on each vehicle's paint. Here are some general considerations:

Size of Clay Bar: Most clay bars are designed to be cut into smaller pieces for use. A standard clay bar can typically be divided into smaller sections, each suitable for one or more cars.

Contamination Level: Lightly contaminated cars will require less clay bar usage compared to heavily contaminated ones. If the cars are regularly maintained and lightly soiled, you can use the clay bar for more vehicles.

Clay Bar Maintenance: Proper maintenance of the clay bar between uses is crucial. Kneading the clay bar to expose clean surfaces and storing it properly can extend its usability.

Car Size: Larger cars or vehicles with more surface area (such as SUVs or trucks) may require more clay bar to cover effectively compared to smaller cars.

Practical Usage Estimate:
Average Use: A single standard-sized clay bar can typically be used for about 2 to 4 cars under normal conditions. This assumes moderate contamination levels and appropriate maintenance of the clay bar between uses.
Varied Conditions: Environmental factors, such as air pollution levels and climate, can also affect how quickly a clay bar becomes saturated with contaminants.
Tips for Maximizing Use:
Cutting the Clay Bar: Cut the clay bar into smaller sections before use. This allows you to work efficiently and reduces waste.
Evaluate Contamination: Assess the level of contamination on each car before starting. Lightly contaminated areas may require less clay bar usage.
Store Properly: After each use, store the clay bar in an airtight container or sealed plastic bag to prevent it from drying out or accumulating contaminants.
By following these guidelines and adapting them to your specific car detailing needs, you can effectively use a clay bar across multiple vehicles while maintaining high-quality results in paint surface preparation.