Most factory paint jobs range from 3.5 to 5.5 mils (87 to 137 microns) (this will vary between manufacturers) for this reason, it’s also recommended that paint be measured when buffing since you can’t see how much paint is being removed during the buffing process. If an insufficient thickness of clear remains after polishing premature failures such as fading or delaminating may occur as the colour coat won't be protected from ultra violet (UV) radiation and a warranty issue may develop in the future. Such risks can be alleviated by monitoring and minimizing the amount of top coat removed, which is best done through quick and easy measurements with an electronic paint gauge, and maintaining a record on a paint thickness template.
German and Japanese cars: 4-5 Mils (1 Mil=1000th of an inch)
With the exception of:
Lexus-White and Tan: 5-7 Mils, Lexus- Black and Silver: 4.5-6 Mils
BMW: Silver: 6-7 Mils
FORD: Approx. 5.5-7 Mils
GM Cars and Trucks: Approx. 4.5-6.0 Mils, Jimmy’s and Blazers: approx 7 Mils
Chrysler: Approx. 5.5-7 Mils (Note Sebring hoods are fibreglass)
Dodge Cars: Similar to Chrysler
Dodge Trucks and newer Ram Pick-ups: Cab approx. Mils and the boxes approx 9 Mils
Jaguar: approx. 6-7.5 Mils (but they tend to vary)
Jeep Grand Cherokee: These read approx. 6-8 Mils, Wranglers: approx. 4.5-5.5 Mils
Note- the above are provided for information only
It’s interesting to note that painters must now demonstrate proficiency with an electronic paint thickness gauge in order to become certified to perform refinish warranty work for General Motors Corp. (GM) vehicles.
Paint Thickness Gauge - Paint Film Thickness - Detail University - Auto Detailing Forum