Car emblems and decals use a powerful adhesive. The best way to melt it is by using a heat gun. Put your heat gun to the lowest setting. Then, apply it to the emblem you want to remove.
With the adhesive heated, there are a few different ways to remove the emblem. A large, flat putty or trim knife can help you take this marking off. However, this method can cause the emblem to break.
Emblems usually leave some adhesive behind even after they've been removed. Use a microfiber towel or sponge to get rid of what's left behind.
Now that the remaining adhesive is gone, you can protect the area. If you used an adhesive remover that left a residue, you should first clean that with soapy water.