Their's a huge variable that is a HUGE factor in the kind of results you get no matter what product you're using on a car and that is the PAINT SYSTEM on the car. Cars painted on the assembly line use different paint systems between manufactures, models and even the same model can have a different paint system used today than was used last year.
Body shops spray "paint systems", that is a brand and type of paint and paint companies, just like computer companies, are continually improving and changing their formulas, so the PPG "paint system" sprayed today can be different than the same PPG product code/paint system sprayed 2 years ago.
Some paints can be marred or scratched, called clay haze by claying while others are not affected. It all has to do with the characteristics of the paint and paint systems are huge variables when it comes to working and detailing your car.
One thing a person can do before claying an entire car, especially if it's the first time they've worked on this particular car, which is a another way of saying, worked on this particular paint system is to do what I call a Test Spot.
Test the clay and clay lube you're using to one small area and then inspect the results in good lighting and even two different kinds of light. If the results look good then keep claying the car. If you see any kind of problem then stop and evaluate the situation, even come to this forum and describe what you're seeing.
And I agree with Chad that a safe practice is to only clay if and when you were already planning on polishing the paint. That's a safe practice but it's not necessary for everyone and for every paint system.
Here's an article I wrote recently that talks about different paint systems...
Hologram Free with a Rotary Buffer
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