Depending on the contaminants in or on your paint (overspray, debris, sap, environmental fallout), you may need a more agressive grade of clay, most car owners will be okay with a fine or medium grade clay bar.
Different Clay Bar Grades
Fine clay bars tend to be the easiest to use simply because the clay is softer. Fine clay is great for a lightly contaminated finish, but not so great at removing things like sap and overspray. If you clay your car regularly, you shouldn’t need anything more than a fine grade clay bar.
Medium clay is more aggressive than fine and will almost certainly microscopically mar the surface as you’re claying because it weighs more. Medium clay, being more firm and dense, will remove stubborn debris and contaminants that fine clay cannot. For the most part, when you clay with a medium grade clay bar you should always polish afterward.
Heavy clay bars really aren’t recommended unless you’re dealing with overspray or other hard to remove contaminants. While heavy clay is often considered overly aggressive for clear coats, it is great on metal wheels and glass. Since these surfaces are much harder than your car’s paintwork, clay works just as good without as much harm. When it comes to paint, just be sure you absolutely have to use the heavy grade bar by first trying medium or light clay to cure whatever is ailing your finish.
Available in Fine 100g, Medium 100g and Heavy 80g.