When should I clay bar my car?
Any time you feel your paint after properly washing and drying it and it feels gritty you should clay bar.
A neat trick to truly tell if your paint is gritty and contaminated is to put your hand inside a plastic bag (shopping or sandwich, doesn’t matter) like it’s a glove and rub your paint. This will amplify any imperfections. Paint that felt somewhat smooth to your bare hand will feel like sand through the bag.