I recently attended a parish mission, where afterwards the priest proceeded outside and blessed all the cars of those attending (in addition to various other objects people brought for a blessing). My concern is what do I do now if I ever need a new car? Can I trade in my car? Must I bury or burn it? Or can a blessing be removed? What is proper to do in this situation?
Ordinarily, sacramentals should be burned (if burnable) or broken up and the ashes or fragments buried. But this assumes that the blessed objects are objects that it is reasonable to burn or destroy. Living creatures (e.g., an animal) or extraordinarily large or valuable items (e.g., a car, a diamond ring) that cannot – indeed, should not – be destroyed and buried when the original owner no longer wants them are dealt with differently.
Canon law provides that sacred places can be relegated to secular use by the competent ordinary or “in fact”:
Sacred places lose their dedication or blessing if they have been destroyed in large part, or have been turned over permanently to profane use by decree of the competent ordinary or in fact (canon 1212, Code of Canon Law).
By analogy, with just cause you can relegate a blessed object to secular use by your choice to do so (i.e., “in fact”). Then you are free to do with it as you will, providing the use you intend is just. In the case of a car, this would mean that a blessed car that you relegated to secular use could be sold, traded in, donated to a charity, or turned into scrap by a junk dealer.
The Ring Cycle by Jimmy Akin