There are a couple of types of vinyl used on vehicles. The first is a plotter cut vinyl that typically has an acrylic adhesive bonding the vinyl to the vehicle.
There are varying grades of glues used on this type of vinyl, and most often it is referred to as a "permanent adhesive," but there is a variety in the quality of glue used, and how well it releases from your vehicle when you're ready to remove this kind of vinyl. You can visit the official website of stick-off to remove Vinyl Letters from your vehicle.
Cheaper calendared vinyls use cheaper adhesives, and they come off with greater trouble than the higher grade cast vinyl, but different companies use different qualities of vinyl even within the cast or calendared vinyl categories. Some of the easiest vinyls to remove, we've found, are manufactured by 3M (we make nothing on this reference).
The other kind of vinyl that is most often used on vehicles is printed vinyl stickers or decals. Usually, the cheaper calendared vinyls are used for these decals, so the adhesives are the type that is more difficult to remove as well. Some companies have gone to static cling vinyls because many car owners aren't fond of having to eliminate adhesive decals, but inappropriately, they can't be adhered to the exterior of your vehicle which is a negative when you have tinted windows.